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Physics 214 Problems
This document is a set of sample problems from
Chapters 2 – 19 and is intended to be a guide in
preparing for the final exam
Final exam Monday Dec 12th 7 - 9pm Phys 114
5/8/2017
Physics 214 Fall 2010
1
Avge/instantaneous
Speed/velocity
Constant
acceleration
s = d/t
v = v0 + at
x = x0 + v0t + 1/2at2
v2 = v02 + 2ax
Gravity/Projectiles
Vectors
Forces
Circular motion
Velocity
Acceleration
Force
momentum
F = ma
F = mv2/r
F = Gm1m2/r2
Gravitation
5/8/2017
Gm1m2/r2 = mv2/r
Physics 214 Fall 2010
Making a trip
Quarter mile drag race
Vertical with gravity
Horizontal velocity is
constant. Acceleration is
always g down
Simple force diagrams
Apparent weight
Horizontal circle
Car around corner
Ferris wheel
Force between two
masses
Planets
2
Conservation of energy
Work
K E = 1/2mv2
Sled sliding down a hill
2
PE =mgh or 1/2kx Work can be negative
W = Fd
Power
Power = P = W/t
Momentum
P = mv
Impulse
FΔt = Δp
Rotation
Constant angular accn
ω = ω0 + αt
θ = ω0t + 1/2αt2
Torque
Kinetic energy
Angular momentum
Τ = Fl = Iα
1/2 Iω2
L = Iω
Energy
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Physics 214 Fall 2010
Motors, lifting
something
Cons of momentum
Two objects collide
Two objects separate
Circle = 2π
Counterclock is +
Wrench
Cons of ang mom
Skater, changing I
3
Pressure
P = F/A
Hydraulic jack
F1/A1 = F2/A2
1.013 105 Pa
Atmospheric pressure
76cm Hg
Suction cup
F = PA
Density ρ = mass/unit
volume
m = ρV w = ρVg
Pressure difference
P = W/A = ρgh
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Physics 214 Fall 2010
Transmitted equally
in all directions in a
liquid
Pressure reduces
with altitude
Maximum weight to
lift PA = mg
Object floats if it’s
density is less than
that of the liquid
h is the difference in
height between two
points in a liquid
4
Archimedes
Buoyant force
Buoyant force is
T + Fb = mg the weight of liquid
Fb = ρgV displaced
T
Fb
g
mg
Force and electric
field
The force a charge
feels is qE. E is in
the direction a +
charge would move
Voltage between
two points is the
change in potential
energy/unit charge
Toward a + charge,
(against E) voltage
increases
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Physics 214 Fall 2010
5
Current, voltage,
charge and
resistance
ΔV = ΔPE/q
I = q/t
If a charge plus q
goes to a lower
voltage energy
qV is released
R = ΔV/I
Ohms law
Circuits
ε is the electromotive
force or the voltage
across a battery when
no current is being
drawn. V or ΔV is the
voltage drop between
two points in a circuit
with current I
Series
Parallel
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I = ε/(Rcircuit + Rbattery)
P = εI =
=
P = VI = I2R = V2/R
I2R
ε2/R
R = R1 + R2 + R3
1/R = 1/R1 +1/R2 +1/R3
Physics 214 Fall 2010
Power dissipated
Current is the same
in all parts of the
circuit
Voltage drop is the
same across all
resistors
6
By definition the field
lines enter a south
pole and leave a
north pole
Magnetism
Force on a moving
charge
F = qvBperpendicular
Induction
Magnetic flux
Induced voltage(emf)
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Ф = BperpA
ε = NΔФ/t
Physics 214 Fall 2010
maximum force is when
v is at right angles to B
and the force is zero if v
is parallel to B or v = 0.
Changing magnetic flux
induces a voltage and if
the circuit is closed a
current will flow
(Generators)
7
Transformer
can be step up
or step down
ΔV2/ ΔV1 = N2/N1
Waves
v = λ/T = fλ
Increase force in
a string
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v = √(F/μ)
Physics 214 Fall 2010
Traveling wave,
can be
longitudinal (e.g.
sound) or can be
transverse (e.g.
on a rope)
Tuning a piano
8
Standing Waves
on a violin string
Fund f = v/λ = v/2L
2nd Har f = v/λ = v/L
3rd Har f = v/λ = 3v/2L
Fund f = v/4L
2nd Harm f = 3v/4L
3rd Harm f = 5v/4L
Organ pipe open
at one end
Frequency is
higher as car
approaches
Doppler effect
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Physics 214 Fall 2010
9
Interference
requires two light
beams
Interference
Bright fringes are
located at
positions given by
dy/x = nλ
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Physics 214 Fall 2010
10
Nucleus of protons
and neutrons
surrounded by
electrons
Atoms
charge
mass
Proton 1.6 x 10-19 1.672 x 10-27kg
Neutron
0
1.675 x 10-27kg
Electron -1.6 x 10-19 9.1 x 10-31kg
Photon
0 E = hf p = h/λ
h = Planck’s const = 6.626 x 10-34J.s
Nuclei
At #N
mass #
After each half life half
the sample has decayed
The amount remaining
after N half lives is
½x½x½…
Radioactive decay
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atomic number =
number of protons
(= number of electrons)
mass number = number
of protons + neutrons
Physics 214 Fall 2010
11
Fusion – join two
light elements
Fission and fusion
Fission – break up a
heavy element
E = mc2
Naturally occurring
uranium is U238
together with a
small amount of
U235. Enrichment is
the separation of
U235 to obtain a pure
sample.
Chain reaction
requires U235
or plutonium
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Physics 214 Fall 2010
12
Q15 A car just starting up from a stop sign has zero velocity at the
instant that it starts. Must the acceleration of the car also be zero at
this instant?
NO.There has to be acceleration otherwise the car would not move
Q17 A racing sports car traveling with a constant velocity of
100 MPH due west startles a turtle by the side of the road who
begins to move out of the way. Which of these two objects is
likely to have the larger acceleration at that instant? Explain.
The turtle. The car has zero acceleration
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Physics 214 Fall 2010
13
Q19 A car moves along a straight line so that its position (distance
from some starting point) varies with time as described by the
graph shown here.
A. Does the car ever go backward?
Yes, at the end
B. Is the instantaneous velocity at point A greater or less than that
at point B?
It is greater at A
d
B
A
t
Q20 For the car whose distance is plotted against time in Q19, is
the velocity constant during any time interval shown in the graph?
In each part of the journey the velocity is constant
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Physics 214 Fall 2010
14
Ch 2 #14
-
d
v0 = 5 m/s
a = 1.2 m/s2
What is the final velocity?
What distance is covered?
+ x
t = 2 sec
a) v = v0 +at = 7.4 m/s
b)
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d = v0t + ½ at2 = 12.4 m
Physics 214 Fall 2010
15
Ch 2 CP4
-
d
+ x
v0 = 14 m/s
a = 2 m/s2
v = 24m/s
What is the time?
What is the distance?
Computed at 1 second intervals.?
a) v = v0 + at
t = 5s
b) d = v0t + ½ at2
c) 1 sec = 15
5/8/2017
= 95m
2 sec = 32
3 sec = 51 m
Physics 214 Fall 2010
4 sec = 72
16
Q14 A ball is thrown straight upward. At the very top of its flight,
the velocity of the ball is zero. Is its acceleration at this point also
zero? Explain.
No the acceleration is 9.8m/s2 down
Q15 A ball rolls up an inclined plane, slows to a stop, and then
rolls back down. Do you expect the acceleration to be constant
during this process? Is the velocity constant?
The acceleration is constant the velocity is not
Q19 Is it possible for an object to have a horizontal component of
velocity that is constant at the same time that the object is
accelerating in the vertical direction? Explain by giving an
example, if possible.
Yes a projectile
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Physics 214 Fall 2010
17
Ch 3 E8
Ball thrown up at 15 m/s
a) How high after 1 second?
b) How high after 2 seconds?
t = 1.53 s
g
+
t=2s
15 m/s
After 1 sec
d = v0t + ½ at2 = 15 – 4.9 = 10.1 m
After 2 sec
d = 15 x 2 – ½ 9.8 x 22 = 10.4 m
Time to top
v = v0 + at
Height at top
5/8/2017
t = 15/9.8 = 1.53 s
d = 11.48m
Physics 214 Fall 2010
18
Ch 3 E10
V0 = 18 m/s
a = - 2 m/s2
a) What is v after 4 seconds?
b) What is time to top?
a=2m/s2
+
18 m/s
a) v = v0 + at
= 18 – 2 x 4 = 10m/s
b) v = 0
5/8/2017
t = 18/2 = 9s
Physics 214 Fall 2010
19
Ch 3 E16
V0v = 30 m/s V0H = 30 m/s
g = - 9.8m/s2
a) What is time to top?
b) What is the range?
a) v = v0 + at
g
30 m/s
+
30 m/s
t = 30/9.8 = 3.06s tR = 6.12s
b) d = 30 x tR = 183.6m
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Physics 214 Fall 2010
20
Ch 3 CP2
V01 = 0 m/s
V02 = 12 m/s
a) What are the velocities after 1.5s?
b) How far has each ball dropped in 1.5s?
c) Does the velocity difference change?
1
2
12 m/s
a) v1 = at = 9.8 x 1.5 = 14.7m/s
v2 = 12 + 9.8 x 1.5 = 26.7m/s
b) d1 = ½at2 = 11.03m
d2 = v2t + ½at2 = 29.03m
c) No
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Physics 214 Fall 2010
21
Questions Chapter 4
Q8 A 3-kg block is observed to accelerate at a rate twice that of a
6-kg block. Is the net force acting on the 3-kg block therefore
twice as large as that acting on the 6-kg block? Explain.
The net force is the same
Q9 Two equal-magnitude horizontal forces act on a box as shown
in the diagram. Is the object accelerated horizontally? Explain.
-F
F
No the net force is zero
Q10 Is it possible that the object pictured in question 9 is moving,
given the fact that the two forces acting on it are equal in size but
opposite in direction? Explain.
Yes, constant velocity
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Physics 214 Fall 2010
22
Q18 The acceleration due to gravity on the moon is approximately
one-sixth the gravitational acceleration near the earth’s surface. If
a rock is transported from the earth to the moon, will either its
mass or its weight change in the process? Explain.
It’s mass will not change but it’s weight wil be 6 times less
Q22 The engine of a car is part of the car and
Ftire
cannot push directly on the car in order to
accelerate it. What external force acting on the
car is responsible for the acceleration of the car
on a level road surface? Explain.
Fair
Freaction
It’s the reaction force between the tires and the road
Q23 It is difficult to stop a car on icy road surface. It is also
difficult to accelerate a car on this same icy road? Explain.
Because of a lack of friction the wheels will skid or spin
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Physics 214 Fall 2010
23
Q31 Two blocks with the same mass are connected by a string
and are pulled across a frictionless surface by a constant force, F,
exerted by a string (see diagram).
A. Will the two blocks move with constant velocity? Explain.
B. Will the tension in the connecting string be greater than, less
than, or equal to the force F? Explain.
F
A. They will accelerate F = ma
B. The tension will be less
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Physics 214 Fall 2010
24
Q33 If you get into an elevator on the top
floor of a large building and the elevator
begins to accelerate downward, will the
normal force pushing up on your feet be
greater than, equal to, or less than the force
of gravity pulling downward on you?
Explain.
+
N
g
N – mg = ma but a is negative so N is smaller than mg
The only force pulling you down is gravity so if you are
accelerating down the force due to gravity must be larger
than the reaction force N ( N is apparent weight)
5/8/2017
Physics 214 Fall 2010
mg
a
25
Ch 4 E4
A 2.5kg block is pulled
with a force of 80N and
friction is 5N
a) What is the
acceleration?
5N
2.5 kg
Net force = 75 N
5/8/2017
80 N
a = 75/2.5 = 30 m/s2
Physics 214 Fall 2010
26
Ch 4 E14
A 4kg rock is dropped and experiences
air resistance of 15N
a) What is the acceleration?
4 kg
15 N
Mg
F = 4 x 9.8 – 15
F = ma = 24.2 N
a = 24.2/4 = 6.05m/s2
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Physics 214 Fall 2010
27
Ch 4 CP4
A 60kg crate is lowered from a height of 1.4m
and the tension is 500N
a) Will the crate accelerate?
b) What is the acceleration?
c) How long to reach the floor?
d) How fast does the crate hit the floor?
a) Net Force
= 60 x 9.8 – 500
= 588 – 500
g
60 kg
= 88 N
b) Will accelerate down
a = 88/60 = 1.47 m/s2
c) d = 1/2 at2
t = 1.38s
d) v = v0 + at
v = 2.03 m/s
5/8/2017
500 N
Physics 214 Fall 2010
28
Ch 4 CP6
A 60kg person accelerating down at 1.4m/s2
a) What is the true weight?
b) What is the net force?
c) What is N?
d) What is the apparent weight?
e) a, b, c, d with 1.4m/s2 up?
a) True weight = mg
N
1.4 m/s2
Mg
= 60 x 9.8 = 588 N
b) Net Force = Ma = 84 N
c) N = 588 – 84 = 504 N
d) 504 N
e) ↑1.4 m/s2
Net Force = 84 N↑
5/8/2017
N = 588 + 84 = 672 N
Physics 214 Fall 2010
W = 672 N
29
Questions Chapter 5
Q6 A ball on the end of a string
is whirled with constant speed in
a counterclockwise horizontal
circle. At point A in the circle, the
string breaks. Which of the
curves sketched below most
accurately represents the path
that the ball will take after the
string breaks (as seen from
above)? Explain.
4
•
3
2
A
1
Path number 3
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Physics 214 Fall 2010
30
Q12 If a ball is whirled in a vertical circle with constant speed, at
what point in the circle, if any, is the tension in the string the
greatest? Explain. (Hint: Compare this situation to the Ferris wheel
described in section 5.2).
The tension is the greatest at the bottom because the
string has to support the weight and provide the force
for the centripetal acceleration.
Q19 Does a planet moving in an elliptical orbit about the sun
move fastest when it is farthest from the sun or when it is nearest
to the sun? Explain by referring to one of Kepler’s laws.
When it is nearest
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31
Q20 Does the sun exert a larger force on the earth than that exerted
on the sun by the earth? Explain.
The magnitude of the forces is the same
they are a reaction/action pair
Q23 Two masses are separated by a distance r. If this distance is
doubled, is the force of interaction between the two masses
doubled, halved, or changed by some other amount? Explain.
The force reduces by a factor of 4
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32
Ch 5 CP 2
A Ferris wheel with radius 12 m makes one complete
rotation every 8 seconds.
a) Rider travels distance 2r every rotation. What speed do riders
move at?
b) What is the magnitude of their centripetal acceleration?
c) For a 40 kg rider, what is magnitude of centripetal force to keep him
moving in a circle? Is his weight large enough to provide this
centripetal force at the top of the cycle?
d) What is the magnitude of the normal force exerted by the seat on the
rider at the top?
e) What would happen if the Ferris wheel is going so fast the weight of
the rider is not sufficient to provide the centripetal force at the top?
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Physics 214 Fall 2010
33
Ch 5 CP 2 (con’t)
a) S = d/t = 2r/t = 2(12m)/8s = 9.42 m/s
Fcent
b) acent = v2/r = s2/r = (9.42m/s)2/12m = 7.40 m/s2
c) Fcent = m v2/r = m acent = (40 kg)(7.40 m/s2) = 296 N
W = mg = (40 kg)(9.8 m/s2) = 392 N
Yes, his weight is larger than the centripetal force required.
d) W – Nf = 296
N = 96 newtons
N
e) rider is ejected
W
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Physics 214 Fall 2010
34
Ch 5 CP 4
A passenger in a rollover accident turns through a radius of
3.0m in the seat of the vehicle making a complete turn in 1
sec.
a) Circumference = 2r, what is speed of passenger?
b) What is centripetal acceleration? Compare it to gravity (9.8
m/s2)
c) Passenger has mass = 60 kg, what is centripetal force
required to produce the acceleration? Compare it to
passengers weight.
a) s = d/t = 2(3.0m)/1 = 19m/s
b) a = v2/r = s2/r = (19 m/s)2/3m = 118 m/s2 = 12g
3m
c) F = ma = (60 kg)(118 m/s2) = 7080 N
F = ma = m (12 g) = 12 mg = 12 weight
5/8/2017
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35
Questions Chapter 6
Q1 Equal forces are used to move blocks A and B across the
floor. Block A has twice the mass of block B, but block B moves
twice the distance moved by block A. Which block, if either, has
the greater amount of work done on it? Explain.
Work is Force times distance so the most work is done on B
Q3 A string is used to pull a wooden block
across the floor without accelerating the block.
The string makes an angle to the horizontal.
A. Does the force applied via the string do work
on the block?
F
d
B. Is the total force involved in doing work or just
a portion of the force?
A. Yes B. just the horizontal component
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36
Q4 In the situation pictured in question 3, if there is a frictional
force opposing the motion of the block, does this frictional
force do work on the block? Explain.
Yes it does negative work since force is opposite the motion
Q8 A woman uses a pulley, arrangement to lift a heavy crate. She
applies a force that is one-fourth the weight of the crate, but moves
the rope a distance four times the height that the crate is lifted. Is
the work done by the woman greater than, equal to, or less than the
work done by the rope on the crate? Explain.
The product Fd is the same for both and the work is equal
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37
Ch 6 E 8
5.0 kg box lifted (without acceleration) thru height of 2.0 m
a) What is increase in potential energy?
b) How much work was required to lift box?
a) PE = mgh PE = PEfinal – PEinitial
= mg(ho+2.0m) – mgho = mg(2.0m)
= (5.0 kg)(9.8 m/s2)(2.0m) = 98J
b) F = ma = 0 = Flift – mg
Flift = mg = (5.0kg)(9.8m/s2) = 49N
W = Fd = (49N)(2.0m) = 98J
5/8/2017
Physics 214 Fall 2010
M
ho+2.0m
M
g
Flift
M
mg
38
Ch 6 CP 2
100 kg crate accelerated by net force = 50 N applied for 4 s.
a) Use Newton’s 2nd Law to find acceleration?
b) If it starts from rest, how far does it travel in 4 s?
c) How much work is done if the net force = 50 N?
a) F = ma a = F/m = 50N/100kg = 0/5 m/s2
M
Fnet
b) d = v0t + ½at2 = ½(0.5)(4)2 4m
c) W = Fd = (50N)(4m) = 200J
d) v = v0 + at = 0 + (0.5 m/s2)(4s) = 2m/s
e) KE = ½mv2 = ½(100kg)(2m/s)2 = 200 J
work done equals the kinetic energy.
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39
Questions Chapter 7
Q5 Are impulse and momentum the same thing? Explain.
No impulse changes momentum
Q6 If a ball bounces off a wall so that its velocity coming back has
the same magnitude that it had prior to bouncing:
A. Is there a change in the momentum of the ball? Explain.
B. Is there an impulse acting on the ball during its collision with the
wall? Explain.
A. Yes momentum is a vector
B. Yes a force acts for a short time
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40
Q17 A compact car and a large truck have a head-on collision.
During the collision, which vehicle, if either, experiences:
A. The greater force of impact? Explain.
B. The greater impulse? Explain.
C. The greater change in momentum? Explain.
D. The greater acceleration? Explain.
A. The forces are equal and opposite
B. The impulse for each is the same
C. The momentum changes are equal and opposite
D. F = ma so a is larger for the compact car
Q22 Is it possible for a rocket to function in empty space (in a
vacuum) where there is nothing to push against except itself?
Yes. It ejects material at high velocity and momentum conservation
means the rocket recoils
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41
Q23 Suppose that you are standing on a surface that is so slick that
you can get no traction at all in order to begin moving across this
surface. Fortunately, you are carrying a bag of oranges. Explain
how you can get yourself moving.
Throw the oranges opposite to the direction you wish to move
Q24 A railroad car collides and couples with a second railroad
car that is standing still. If external forces acting on the system
are ignored, is the velocity of the system after the collision equal
to, greater than, or less than that of the first car before the
collision?
The velocity after is exactly half
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42
Ch 7 E 8
A ball has an initial momentum = 2.5 kg m/s, it bounces
off a wall and comes back in opposite direction with
momentum = -2.5 kg m/s
a) What is the change in momentum of the ball?
b) What is the impulse?
a) Δp = pf – pi = -2.5 – (+2.5) = - 5kgm/s
Pi = 2.5kgm/s
b) Impulse = Δp = - 5kgm/s
F
Pf = -2.5kgm/s
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+
43
Ch 7 E 10
M1 and M2 collide head on
a) Find initial momentum of M1 and M2
b) What is the total momentum of the system before
collision?
c) Ignore external forces, if they stick together after
collision, which way do the masses travel?
west M2 = 80kg
6.0m/s
3.5m/s
a) p1 = -100 x 3.5 = 350kgm/s
M1 = 100kg
east
p2 = 80 x 6 = 480kgm/s
b) Total momentum = 480 – 350 = 130kgm/s east
c) The masses will travel east with p = 130kgm/sec
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44
Ch 7 CP 2
A bullet is fired into block sitting on ice. The bullet travels at
500 m/s with mass 0.005 kg. The wooden block is at rest with a
mass of 1.2 kg. Afterwards the bullet is embedded in the block.
a) Find the velocity of the block and bullet after the impact (assume
momentum is conserved).
b) Find the magnitude of the impulse on the block of wood.
c) Does the change in momentum of the bullet equal that of wood?
a) pfinal = pinitial = (0.005 kg)(500 m/s)
m
v
M
pfinal = (Mbullet + Mwood)v = 2.5 kg m/s
No friction (ice)
v = (2.5 kg m/s)/(1.205 kg) = 2.07 m/s
b) Impulse = Δp = pfinal – pinitial
= (1.2 kg)(2.07 m/s) – 0 = 2.50 kg m/s
c) Δp for bullet = (0.005 kg)(500 m/s) – (0.005 kg)(2.07 m/s)
= 2.50 kg m/s
Momentum is conserved, so momentum lost by bullet is gained
by wood.
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45
Questions Chapter 8
Q6 Is the linear speed of a child sitting near the center of a
rotating merry-go-round the same as that of another child sitting
near the edge of the same merry-go-round? Explain.
The angular velocity is the same but v = ωr, so speed is greatest at the edge
Q11 The two forces in the diagram have the same magnitude.
Which orientation will produce the greater torque on the wheel?
F1
Explain.
F
2
F1 because it is the tangential component that produces the torque
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46
Q13 Is it possible for the net force acting on an object to be zero,
but the net torque to be greater than zero? Explain. (Hint: The
forces contributing to the net force may not lie along the same
line.)
F
F
Q20 Two objects have the same total mass, but object A has its
mass concentrated closer to the axis of rotation than object B.
Which object will be easier to set into rotational motion? Explain.
A has a smaller moment of inertia and torque = Iα so will accelerate faster
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47
Q26 A child on a freely rotating merry-go-round moves from near
the center to the edge. Will the rotational velocity of the merrygo-round increase, decrease, or not change at all? Explain.
L =Iω so I increases and ω will decrease. This requires work
Q29 Suppose you are rotating a ball attached to a string in a
circle. If you allow the string to wrap around your finger, does
the rotational velocity of the ball change as the string shortens?
Explain.
L =Iω so I decreases and ω will increase. This requires work
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48
Ch 8 E 6
Rotational velocity decreases from 6 rev/s to
3 rev/s in 12 s.
What is rotational acceleration?
w = wf – wi = 3rev/s – 6rev/s = - 3rev/s
= w/t = (-3rev/s)/12s = -1/4 rev/s2
 = -1/4 rev/s | 2rad/rev = -/2 rad/s2
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Ch 8 CP 10
5N placed 10 cm from fulcrum of balance beam,
what weight should be put 4 cm from fulcrum on
other side to balance
 = Fl = 0 = -(5N)(10cm) + x(4cm)
x = 50Ncm/4cm = 12.5 N
?
4cm
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10cm
50
Ch 8 CP 4
See Fig 8.23. A student sits on a stool with wheels with a bike
wheel with Ib = 2kgm2 and wb = 5 rev/s. Bike wheel is spinning,
student is not. The student on stool with bike wheel: Is = 6 kgm2.
a) Initially, what is L?
b) Student flips bike wheel. What is student’s L?
c) Where does the torque come from that accelerates student?
a) Lb = Ib wb (just the bike wheel spinning).
wb = 5 rev/s 2/rev = 10 rad/s
Lb = 20 kg m2/s , upwards
b) L = Lb + Ls (flipped bike wheel plus student).
-20 kg m2/s + Is ws = +20 kg m2/s Ls = +40 kg m2/s
c) Student supplies torque when he flips bike wheel.
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Questions Chapter 9
Q1 Is it possible for a 100-lb woman to exert a greater pressure on
the ground than a 250-lb man? Explain.
Yes. The pressure will be mg/A so if A is small e.g. small
heels the pressure will be very large
Q3 The same force is applied to two cylinders that contain air.
One has a piston with a large area, and the other has a piston with
a small area. In which cylinder will the pressure be greater?
The pressure is F/A so the one with the smallest A
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Q15 Is it possible for a solid metal ball to float in mercury?
The upward force is the weight of liquid displaced and the
downward force is the weight of the ball. If the density of the
liquid is greater than that of the ball it will float.
Q16 A rectangular metal block is suspended by a string in a
breaker of water so that the block is completely surrounded by
water. Is the water pressure at the bottom of the block equal to,
greater than, or less than the water pressure at the top of the
block?
The pressure is ρgh so the pressure is higher at the bottom. The
difference in pressure provides the upward force on the block
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Q19 A large bird lands on a rowboat that is floating in a swimming
pool. Will the water level in the pool increase, decrease, or remain
the same when the bird lands on the boat?
The buoyant force is the weight of liquid displaced so to
support a larger weight more liquid is displaced and the level
rises
Q20 A rowboat is floating in a swimming pool when the anchor
is dropped over the side. When the anchor is dropped, will the
water level in the swimming pool increase, decrease, or remain
the same?
When the anchor is in the boat it’s whole weight is supported and the
amount of water displaced balances that weight. When it is thrown
overboard it sinks and only displaces it’s volume so the water level
falls
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Ch 9 E 4
Pressure of gas in piston = 300 N/m2.
Area of Piston = 0.2m2.
What is force exerted by piston on gas?
A = 0.2m2
p = 300 N/m2
P = F/A, F = PA = 300 N/m2 (0.2 m2) = 60 N
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Ch 9 E 6
Hydraulic system: A2 = 50 A1
F2 = 6000 N. What is F1?
F2 = 6000N.
A1
A2
Pressure is the same just underneath each piston
F1/A1 = F2/A2
F2/F1 = A2/A1 = 50A1/A1 = 50
F1 = F2/50 = 6000/50 = 120N
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Ch 9 E 12
Boat displaces 2.5 m3 of water.
Density of water H2O = 1000 kg/m3.
a) What is the mass of water displaced?
b) What is the buoyant force?
a) Mass of fluid displaced
(mFD) = volume x density of fluid.
MFD = VFDH2O = (2.5 m3)(1000 kg/m3) = 2500 kg
Fb = WFD
b) Buoyant force equals weight of fluid displaced.
Fb = WFD = mFD g = (2500 kg)(9.8 m/s2) = 24500 N
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Ch 9 CP 2
Water density = H2O = 1000 kg/m3. Depth of swimming pool = 3m.
a) What is the volume of a column of water 3m deep and cross
sectional area 0.5 m2?
b) What is its mass?
c) What is its weight?
d) What is the excess pressure exerted on the pool bottom?
e) Compare to atmospheric pressure.
a) V = Ad = (0.5 m2)(3m) = 1.5 m3
b) M = V = (1.5 m3)(1000 kg/m3) = 1500 kg
c) W = Mg = (1500 kg)(9.8 m/s2) = 14700 N
0.5m2
3m
d) P = F/A = 14700N/0.5m2 = 29400 Pa
e) Atmospheric Pressure is about 100 kPa
P is about 30 kPa
P/Atm = (29400 Pa)/(1.013 x 105 Pa) = 0.29
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Ch 9 CP 4
Wooden boat: 3m x 1.5m x 1m that carries five people.
Total mass of boat and people equals 1200 kg.
a) What is total weight?
b) What is buoyant force required to float?
c) What volume of water must be displaced to float?
d) How much of the boat underwater?
a) W = Mg = 1200 kg (9.8 m/s2)
W = 11760 N
1m
3m
b) Fnet = Fb – W = 0
Fb = 11760 N
W
c) Fb = H2O Vg (see Ch 9 E 12)
Fb/H2Og = 11760N/(1000 kg/m3)(9.8 m/s2) = V = 1.2 m3
d) V = LWh = (3m)(1.5m)h = 1.2 m3
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Questions Chapter 10
Q1 Is an object that has a temperature of 0°C hotter than, colder
than, or at the same temperature as one that has a temperature of
0°F?
Water freezes at 0o C and 32o F so 0o F is colder
Q2 Which spans a greater range in temperature, a change in
temperature of 10 Fahrenheit degrees or a change of 10
Celsius degrees?
There is 100o C between water freezing and boiling and
180o F so 1oC = 1.8oF so a change of 10oC is larger
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Q21 An ideal gas is compressed without allowing any heat to flow
into or out of the gas. Will the temperature of the gas increase,
decrease, or remain the same in this process?
The temperature will increase ΔU = W
Q23 Heat is added to an ideal gas, and the gas expands in the
process. Is it possible for the temperature to remain constant
in this situation?
Yes. This is an isothermal expansion and W = Q
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Q25 Heat is added to a hot-air balloon causing the air to
expand. Will this increased volume of air cause the balloon to
fall?
Archimedes principle states that the buoyant force is equal to the
weight of liquid displaced. So if the balloon stays the same size
and as the air expands it leaves the balloon it will rise faster
because the weight of the air inside will be less. If no air escapes
but the balloon increases in size it will also rise because the
buoyant force is larger
Q27 A block of wood and a block of metal have been sitting on a
table for a long time. The block of metal feels colder to the touch
than the block of wood. Does this mean that the metal is actually
at a lower temperature than the wood?
No. What you feel is heat flow and the thermal conductivity of metal is much
bigger than that of wood. This is also why you feel much colder when the
air is damp and why trapped dry air in fiberglass is used for insulation. It is
also because room temperature is lower than body temperature
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Ch 10 E 2
Temperature is 14° F.
What is the temperature in Celsius?
Tc= 5/9 (TF – 32) = 5/9 (14 - 32)=5/9 (-18) = -10° C
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Ch 10 E6
How much heat does it take to raise the temperature
of 70 g of H2O from 20°C to 80°C? C= 1 cal/gram/oC.
Q = mcT=(70)(1)(80-20) = 4200 cal
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Ch 10 E 12
Add 600 J to 50 g of H2O initially at 20°C
a) How many calories?
b) What is the final temperature of the H2O
a) 600 /4.186 = 143.3 cal = Q
b) Q=mcT
T=Q/mc=143.3/(50)(1)=2.87°C
TF=22.87°C
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Ch 10 E 16
Add 500 cal of heat to gas. Gas does 500 J of
work on surroundings.
What is the change in internal energy of gas?
U = Q-W
Q = 500/ 4.186 = 2093 J
W=500 J
U = 2093 – 500 = 1593 J
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Ch 10 CP 4
150 g of metal at 120°C is dropped in a beaker containing 100 g H2O
at 20°C. (Ignore the beaker). The final temperature of metal and water
is 35°C.
a) How much heat is transferred to the H2O?
b) What is the specific heat capacity of metal?
c) Use the same experimental setup – how much metal at 120°C to have final
temperature of metal and water = 70°C?
a) Q = mcT = (100)(1)(35-20) = 1500 cal
b) Q = mcT → c = Q/mT =
c = -1500/(150)(35-120) = 0.12 cal/gram/°C
c) Q H2O = mcT = (100)(1)(70-20) = 5000 cal
Q metal = - Q H2O = - 5000
Q metal = mcT; m = Q metal/cT = -5000/(0.12)(70-120)
m = 833 g
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Ch 11 E 6
A Carnot engine takes in heat at 650 K and releases
heat to a reservoir at 350K.
What is the efficiency?
ec = (TH – Tc) / TH = 650-350 / 650 = 0.46
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Ch 11 CP 2
Carnot engine operates b/w 500° C and 150° C and does
30 J of work in each cycle.
a) What is the efficiency?
b) How much heat is taking in from the high-temp reservoir each cycle?
c) How much heat is released to low-temp reservoir each cycle?
d) What is the change, if any, in the internal energy of gas each cycle?
a) εc= (TH-Tc)/ TH= (500+273.3)-(150+273.3)/(500+273.3) = .045
b) ε = W/QH , QH = W/ε = 30/0.45 = 66.3 J
c) W = QH-Qc, Qc = QH-W = 66.3J - 30J = 36.3J
d) U = Q-W, W = 30J
Q = QH - Qc = 66.3 – 36.3 = 30 J
U = 30-30 = 0
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Q20 Is it possible for an electric field to exist at some point in
space at which there is no charge?
Yes. Electric fields are created by charge but extend to infinity
Q21 Two charges, of equal magnitude but opposite sign, lie along a
line as shown in the diagram. Using arrows, indicate the directions
of the electric field at points A, B, C, and D shown on the diagram.
-q
C
•
-
q
A
•
B
+
•
D
•
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Q23 Three equal positive charges are located at the corners of a
square, as in the diagram. Using arrows, indicate the direction of the
electric field at points A and B on the diagram.
A
q
+
•
+
q
•
B
q
+
Q25 If we move a positive charge toward a negative charge, does
the potential energy of the positive charge increase or decrease?
The potential energy decreases
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Q26 If we move a negative charge toward a second negative
charge, does the potential energy of the first charge increase or
decrease?
It increases because they repel each other it means as you get closer
the force gets larger. You have to do work to bring them closer
Q32 Would you be more likely to be struck by lightning if you stood
on a platform made from a good electrical insulator than if you stood
on the ground?
Standing on an insulator is the safest which is why the safest
place in inside a car because the tires are insulators. It’s also the
same with fallen power lines
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Ch 12 E 8
Electron and proton have charges of equal magnitude,
1.6×10-19C, but opposite signs. If the electron and
proton are separated by R=5×10-11m, what is the
electrostatic (vector) force b/w them?
P
+
e
r
F = kq1q2 / r2 = -(9×109)(1.6×10-19)2 / (5×10-11m)2
F = 9.22 × 10-8 N towards proton
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CH 12 E14
Charge q = -4 × 10-6 c placed in Electric field of
E = 8.5 × 104 N/C
Towards right. What is the electrostatic
(vector) force on charge q?
E
9m
F = qE = (4×10-6)(8.5×104)
F = 0.34 N
Since positive charge moves with field lines and q is
negative, q moves to the left
F = 0.34 N to left
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Ch 12 CP 4
4 equal positive charges located at corners of the square
(see diagram)
a) Use small arrows to indicate direction of electric field at
each labeled point
b) Would the magnitude of electric field be equal to zero at any
labeled point?
a)
+
+
E
+
+
+
B
+
+
A
D
C
+
b) Electric Field is equal to zero at the center of the
square (A).
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Questions Chapter 13
Q3 In a simple battery-and-bulb circuit, is the electric current that
enters the bulb on the side nearer to the positive terminal of the
battery larger than the current that leaves the bulb on the opposite
side?
The current is the same
Q4 Are electric current and electric charge the same thing?
No. electric current is the flow of charge I = dq/dt
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Q11 A dead battery will still indicate a voltage when a good
voltmeter is connected across the terminals. Can the battery still be
used to light a bulb?
A battery has internal resistance so although one can measure an
open circuit voltage when connected to a circuit the voltage will
drop and the current flow will be very low.
Q12 When a battery is being used in a circuit, will the voltage
across its terminals be less than that measured when there is no
current being drawn from the battery? Explain.
The voltage will be less because of the voltage drop due to the
internal resistance
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Q13 Two resistors are connected in a series with a battery as
shown in the diagram. R1 is less than R2.
A. Which of the two resistors, if either, has the greater current
flowing through it? Explain.
B. Which of the two resistors, if either, has the greatest voltage
difference across it? Explain.
R1
Є
R2
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The current is the same in
both. Since V = IR the greatest
voltage drop will be across R2
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Q14 In the circuit shown below, R1, R2, and R3 are three resistors of
different values. R3 is greater than R2, and R2 is greater than R1. Є
is the electromotive force of the battery whose internal resistance
is negligible. Which of the three resistors has the greatest current
flowing through it?
R1
Є
R2
R3
I3 = I1 + I2 so I3 is the largest
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Q15 In the circuit shown in question 14, which of the three
resistors, if any, has the largest voltage difference across it?
V = IR and both I and R are the largest for R3
Q16 If we disconnect R2 from the rest of the circuit shown in the
diagram for question 14, will the current through R3 increase,
decrease, or remain the same?
The resistance of the
circuit will increase
so the current
through R3 will
decrease.
R1
Є
R2
R3
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Q21 Is electric energy the same as electric power?
Power is the rate at which energy is used. Your electrical bill
is for the total energy you use.
Q22 If the current through a certain resistance is doubled, does the
power dissipated in that resistor also double?
P = I2R so the power increases by a factor of 4
Q23 Does the power being delivered by a battery depend on the
resistance of the circuit connected to the battery?
Yes because increasing the resistance lowers the current
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Ch 13 E 14
24  resistor has voltage difference 3V across leads.
a) What is the current through the resistor?
b) What is the power dissipated in resistor?
3V
24 
a) V = IR
I = V/R = 3/24 = 0.125A
b) P = IV = V2/R = (3)2/24 = 0.375W
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Ch 13 E 16
A toaster draws current = 7A on a 100-V AC line
a) What is the power consumption of the toaster?
b) What is the resistance of the heating element
in the toaster?
→ I = 7A
a) P = IV = 7.110 = 770 W
b) V = IR, R = V/I = 110/7 = 15.7 
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R
83
Ch 13 CP 2
Three 30- light bulbs connected in PARALLEL to 1.5
V battery with negligible internal resistance.
a) What is the current through the battery?
b) What is the current through each bulb?
c) If one bulb burns out, does the brightness of the
other bulbs change?
1.5 V
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R
R
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R
R = 30 
84
Ch 13 CP2 cont.
a) 1/Rp = 1/R1 + 1/R2 + 1/R3 = 1/30 + 1/30 + 1/30 = 1/10
Rp = 10 
V = ItRp , It = V/Rp = 1.5/10 = 0.15 A
b) V = IR, I = V/R = 1.5/30 = 0.05 A
Notice that total current, It, through the battery is the sum of
currents through each bulb.
It = 3(I) = 1.5 A
c) Brightness of remaining two bulbs do not change. Instead, load
on the battery is reduced. Each remaining bulb still feels 1.5 V.
So, each remaining bulb still draws 0.05 A of current. Since,
P=IV, each remaining bulb still outputs same power. This is
benefit of hooking circuits in parallel.
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Q6 If we regard the earth as magnet, does its magnetic north pole
coincide with its geographical north pole? What defines the
position of the geographical north pole?
The geographical north pole is defined by the axis of rotation. The
magnetic north pole is determined by the currents and fields in the
iron core of the earth. About every 250,000 years the field of the
earth reverese.
Q7 We visualized the magnetic field of the earth by imagining that
there is a bar magnet inside the earth (fig. 14.7). Why did we draw
this magnet with its south pole pointing north?
The definition of the North pole is the point at which the North pole
of a magnet would point. This means the North pole is a physical
magnetic south pole.
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Q9 A horizontal wire is oriented along an east-west line, and a
compass is placed above it. Will the needle of the compass deflect
when a current flows through the wire from east to west, and if so,
in what direction?
The current will produce a field that appears clockwise looking
west. This means the compass will point north/south
Q11 A uniform magnetic field is directed horizontally toward the
north, and a positive charge is moving west through this field. Is
there a magnetic force on this charge, and if so, in what
direction?
Point index finger along the velocity, the middle finger in the
direction of B and then the thumb points in the direction of the
force. The force points up.
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Q15 If we look down at the top of a circular loop of wire whose plane
is horizontal and that carries a current in the clockwise direction,
what is the direction of the magnetic field at the center of the circle?
The field is perpendicular to the plane in the direction that if you
look in that direction the current is clockwise. So the answer is
down.
Q17 A current-carrying rectangular loop of wire is placed in an
external magnetic field with the directions of the current and field
as shown in the diagram. In what direction will this loop tend to
rotate as a result of the magnetic torque exerted on it?
B
F
B
F
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Q24 A horizontal loop of wire has a magnetic field passing upward
through the plane of the loop. If this magnetic field increases with
time, is the direction of the induced current clockwise or
counterclockwise (viewed from above) as predicted by Lenz’s law?
The current induced produces a magnetic field that opposes the
increase so the induced magnetic field points down so the current
must be clockwise viewed from above.
Q25 Two coils of wire are identical except that coil A has twice as
many turns of wire as coil B. If a magnetic field increases with time at
the same rate through both coils, which coil (if either) has the larger
induced voltage?
The flux in A is twice that in B so the induced voltage is twice as large.
Q28 Does a simple generator produce a steady direct current?
No. As the coil turns at constant angular velocity the rate of
change of flux depends on the angle of the coil to the field so the
current is AC
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Q30 Can a transformer be used, as shown in the diagram below, to
step up voltage of a battery? Explain.
V2/V1 = N2/N1
So if N2 > N1 the voltage
is stepped up.
Q31 By stepping up the voltage of an alternating current source
using a transformer, can we increase the amount of electrical
energy drawn from the source?
No. For an ideal transformer the input power = output power.
In a real transformer energy is lost due to heat. Feel the
transformer for your laptop.
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Ch 14 E 10
Loop of wire enclosing Area, A = 0.03m2, has magnetic
field passing thru its plane at an angle. Component of
magnetic field perpendicular to plane = 0.4T, while
component parallel to plane = 0.6T. What is magnetic
flux thru coil?
I = B1A = 0.4(0.03)
A
= 0.012Tm2
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Ch 14 E 12
Coil of wire with 60 turns and cross-sectional area, A
= 0.02m2, lies with it’s plane perpendicular to B =
1.5T magnetic field. Coil is rapidly removed B-field in
time t=0.2s.
a) What is initial magnetic flux thru coil?
b) What is average voltage induced in coil?
a)
Φ = NB1A = (60)(1.5)(0.02) = 1.8Tm2
b)
ε
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= ΔΦ/t = (1.8 Tm2 – 0)/0.2s = 9V
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Ch 14 CP 4
Transformer is designed to step down line voltage of
110V to 22V. Primary coil has 400 turns of wire.
a) How many turns of wire on secondary coil?
b) Current in primary I1 = 5A. What is max current in
second coil?
c) If transformer gets warm during operation, will current
in secondary coil equal that computed in previous
question (b)?
a) ΔV2/ ΔV1 = N2/N1 , N2 = N1(ΔV2/ ΔV1) = 400(22/110) = 80 turns
b) ΔV2I2 ≤ ΔV1I1
I1 = 110/22 (5) = 25A
Max current in second coil = 25A.
c) No, heat that warms up transformer is power dissipated in the form
P = I2R. Power is lost to heat.
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Q24 Suppose that we increase the temperature of the air through
which a sound wave is traveling.
A. What effect does this have on the speed of the sound wave?
Explain.
B. For a given frequency, what effect does increasing the temperature
have on the wavelength of the sound wave? Explain.
The speed increases and the wavelength increases
Q25 If the temperature in a organ pipe increases above room
temperature, thereby increasing the speed of sound waves in the pipe
but not affecting the length of pipe significantly, what effect does this
have on the frequency of the standing waves produced by this pipe?
The length is unchanged so the wavelength is unchanged
so the frequency increases
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Q26 Is the wavelength of the fundamental standing wave in a tube
open at both ends greater than, equal to, or less than the wavelength
for the fundamental wave in a tube open at just one end?
A tube open at both ends has half a wavelength
whereas the tube open at one end has one quarter of a
wavelength.
Q27 A band playing on a flat-bed truck is approaching you rapidly
near the end of a parade. Will you hear the same pitch for the
various instruments as someone down the street who has already
been passed by the truck?
The pitch increases as the band approaches and decreases
as it is going away
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Ch 15 E 2
Water waves have a wavelength  = 1.4 m and
Period T = 0.8s . What is the velocity of the waves?
v =  / T = 1.4/0.8 = 1.75 m/s
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Ch 15 E 8
String of length 0.8 m is fixed at both ends. The story is
plucked so that there are two nodes along the string in
addition to those at either end. What is the wavelength of
the interfering waves?
fixed
head
node
node
λ
½λ
v
snapshot
T
R
v
At each node wave T and wave R cancel. From the picture a total of 3/2  fit
on 0.8 m string. 3/2  = 0.8 m →  = (2/3) 0.8 = 0.53 m
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Ch 15 E 10
What is the frequency of a sound wave with wavelength
 = 0.68 m travelling in room temperature air (v=340m/s)?
v = f → f = v/ = 340/0.68 m = 500 Hz
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Ch 15 CP 2
A guitar string has length 1.25 m and mass 40 g. After
stringing the guitar, string has 64 cm between fixed
points. It is tightened to tension = 720 N.
a) What is mass per unit length of string?
b) What is wavespeed on tightened string?
c) What is wavelength of traveling waves that interfere to
form the fundamental standing wave?
d) What is frequency of the fundamental standing wave?
e) What are wavelength and frequency of the next
harmonic?
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Ch 15 CP2 cont.
a) =M/L=0.04/1.25=0.032 kg/m
b)  = F/ = 720/0.032 = 22500 = 150 m/s
c)
v
R
=
T
v
node
Snapshot of fundamental
standing wave
antinode
0.64 m = ½ 
 = 1.28 m
node
d) =1.28 m ; f = / = 150/1.28 = 117 Hz
 = 0.64 m
f = / = 150/0.64 = 234 Hz
e)
node anti-node node anti-node node
Snapshot of second harmonic
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Questions Chapter 16
Q3 Is it possible for an electromagnetic wave to travel through a
vacuum?
Yes
Q11 Skylight is produced by scattering of light from the direct
beam coming from the sun. Why is the color of the sky different
from the color of the light of the sun itself?
Blue light is scattered more strongly than red light
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Q12 Two waves interfere to form fringes in Young’s double-slit
experiment. Do these two waves come from the same light
source?
Yes. They must be coherent
Q13 If two waves start out in phase with one another, but one wave
travels half a wavelength farther than the other before they come
together, will the waves be in phase or out of phase when they
combine?
They will be exactly out of phase
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Q15 When light is reflected from a thin film of oil on a water puddle,
the colors we see are produced by interference. What two waves are
interfering in this situation?
One ray is reflected by the top of the oil, the second from the
oil/water interface
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Ch 16 E4
X-rays often have wavelength of about =10-10m. What
is the frequency of such waves?
f = c/ = 31018 Hz
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Ch 16 E 8
Light of 500 nm is reflected from a thin film of air
between two glass plates. The thickness of film:
d=1m=1000 nm.
a) How much farther does light reflected from bottom plate travel than
that reflected from top plate?
b) How many wavelengths of light does this represent?
top
bottom
a) Path difference = 2d
= 2000 nm
b) 2000 nm/ = 4
4 wavelengths of light
d
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Ch 16 CP 2
Light of wavelength =600 nm passes through a double
slit with d = 0.03 mm. The resulting fringe pattern is
observed on a screen 1.2 m from the double slit.
a)
b)
c)
d)
How far from the center of the screen is the first bright fringe?
Second bright fringe?
First dark fringe?
Sketch a picture of the central seven bright fringes (central fringe & 3 on
either side). Clearly indicate the distance from each fringe to the center
of the screen.
d = 0.03 mm
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y1
y
z2 1
x = 1.2 m
Physics 214 Fall 2010
z1- first dark fringe
y1, y2 - first and second
bright fringes
106
Ch 16 CP 2 cont.
a) d y/x=n or yn= n x/d  = n (1.2)/(0.0310-3) (60010-9)
yn=n(0.024)m
y1 = 1(0.024) = 0.024m = 2.4 cm
b) y2 = 2 (0.024) m = 4.8 cm
y3 = +7.2 cm
c) z is spacing nth dark fringe
dz/x = (n-1/2) 
or
zn = (n-1/2) x/d 
zn = (n-1/2) (0.024m)
z1 = (1-1/2)(0.024m) = 1.2 cm
y2 = 4.8 cm
y1 = +2.4 cm
y=0
y-1= -2.4 cm
d) y1 = 2.4 cm
y2 = 4.8 cm
y3 = 3(0.024m) = 7.2 cm
+4
-4
y-2 = -4.8 cm
y-3 = -7.2
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Questions Chapter 18
Q11 Assuming that cathode rays are a beam of charged particles,
how could you demonstrate that these particles are negatively
charged?
By deflection in a magnetic field
Q13 Would you expect X rays to be produced by a television
picture tube?
Yes the accelerated electrons hitting the screen do produce X rays
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Ch 18 E 6
How many electrons are required to produce 1
microcoulomb of negative charge?
e = 1.6 x 10-19C
1 microcoulomb = 10-6C = ne
n = 10-6/(1.6 x 10-19) = 6.25 x 1012 electrons
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Ch 18 E 10
Suppose a photon has wavelength λ = 520 nm
a) What is frequency of photon?
b) What is photon’s energy in Joules?
a) c = fλ , f = c/λ = (3 x 108)/(520 x 10-19) = 5.769 x 1014Hz
b) E = hf = (6.626 x 10-34)(5.769 x 1014) = 3.823 x 10-19J
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Q4 Is it possible for atoms of the same chemical element to have
different chemical properties?
No the chemical properties are determined by the electrons
Q5 Which number, the mass number or the atomic number,
determines the chemical properties of an element?
The atomic number gives the number of electrons
Q7 In a nuclear reaction, can the total mass of the products of
the reaction be less than the total mass of the reactants?
Yes. E = mc2 and mass can be turned into energy
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Q13 In a time equal to two half-lives of a radioactive isotope, would
you expect all of that isotope to have decayed?
NO. In one half life ½ decay so in two half lives ¼ would be left
Q15 Chemical reactions and nuclear reactions can both release
energy. On the average, would you expect the energy released per
unit of mass in a chemical reaction to be greater than, equal to, or
less than what is released in nuclear reaction?
Chemical reactions involve changes in the electron energy
levels and these are very low energy compared to nuclear
reactions
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Q17 Suppose that you light a match to a mixture of oxygen and
hydrogen, which then reacts explosively to form water. Is this a
chemical reaction or a nuclear reaction?
It is a chemical reaction in which two hydrogen atoms and one oxygen
atom join.
Q18 The most common isotope of uranium is uranium-238. Is this
the isotope that is most likely to undergo fission?
NO U235
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Q19 What property of the fission reaction leads to the possibility of
a chain reaction?
The emittance of more than one neutron.
Q21 Do the control rods in a nuclear reactor absorb or emit
neutrons?
They absorb neutrons
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Q22 If you wanted to slow down the chain reaction in a nuclear
reactor, would you remove or insert the control rods?
Insert
Q28 How does nuclear fusion differ from nuclear fission?
Fission is breaking a very heavy element into two lighter
elements
Fusion is joining two very light elements into on heavier element
Both produce energy. Fusion produces the most and is cleaner
but much more difficult
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Q29 Is nuclear fission the main process involved in the energy
generated in the sun?
No, the process is fusion.
Q31 Which can produce larger yields of energy, a fission weapon
or a fusion weapon?
A fusion weapon. The original bomb was a fission bomb. The
hydrogen bomb uses a fission bomb to trigger a fusion bomb.
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Homework problems
This list of
homework
problems is a
guide with
typical
problems from
each of the
chapters 2 - 19
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Assignment
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Problems
1
2,4
3,5
1,3
3,4
2,4
3,4
2
2,4
1,4
1,2,3
2,3,4
4
1,4,5
1,3,4
1,4
1
Physics 214 Fall 2010
Assignment
18
19
20
21
22
23
24
25
26
27
28
Problems
1,3,5
1,5
1,3
1,4
3
1,3
2,4
1,3
2
3,4
2
117