Download 1) - McKinney ISD Staff Sites

1) What is entropy? A measure of disorder in a system
2) A 51kg block of metal has specific heat of 222 J/kgoC. How much heat energy must be applied to the block of
metal to raise its temperature from 10oC to 22oC? Q = 1x105 J
3) A 5kg block of metal has specific heat of 5 J/kgoC. How much heat energy must be applied to the block of
metal to raise its temperature from 1oC to 90oC? Q = 2x103 J
4) A 3g block of metal absorbs 3x103 J of energy during a change in temperature from 20oC to 30oC? What is the
specific heat capacity of the material? c=100 J/goC
5) A 7kg block of metal has specific heat of 5 J/kgoC. It absorbs 8x108 J of energy during a change in temperature?
If the metal started at 15oC what is its final temperature? Tf = 2x107 oC
6) The Earth travels in a circular motion around the Sun. What would its velocity vector be if the gravity between
the Earth and the Sun suddenly ceased to exist? Draw your answer on your answer sheet and verbally explain it
as well.
Objects moving in a circular path have tangential velocity, their inertia will take them on a path
tangential to the original circular path once Fc is removed.
7) Define thermal equilibrium. The point at which average internal energies (Temperatures) of objects in a
system equalize.
8) What is the first law of thermodynamics? A.k.a. The law of conversation of energy. Energy is conserved in a
system (no energy loss)
9) What is the second law of thermodynamics? Entropy is always increasing; Energy is lost as unrecoverable
waste heat.
10) Will there be more, less, or the same amount of entropy in the universe 10 seconds from now? MORE
11) A perfect machine will more closely match which of the following statements?
a. Meet the requirements of the first law and not the second
b. Meet the requirements of the second law of thermodynamics but not the first
c. Will produce more output energy than input energy
12) From the graph above, determine the temperature at which the material solidifies. 30oC
13) From the graph above, determine the temperature at which the material liquefies. 30oC
14) When you walk, you move your mass around. In terms of energy types, your body converts what kind of energy
into what other kind of energy in order to move your body around? Chemical into Mechanical
15) The Hoover dam is useful for a number of reasons, one is energy conversion. Specifically, what kind of energy
does the Hoover dam convert and what kind of energy does it output? GPE into Electrical
16) NASA has launched a deep space probe into the outer reaches of the solar system. It is time to make a course
correction to ensure the probe stays on course. If the radio signal NASA transmits from Houston control takes
10 minutes to reach the probe how far away from Earth is it?
V 
d
t
t *V 
d
*t
t
d  v *t
d  (3.0 *10 8 m s ) * (10 min x
60 sec
)
1 min
d  1.8 *1011 m
17) Construct a detailed figure to represent the electromagnetic spectrum. Label the frequencies and proper
locations of Radio, Infrared, Light, Ultraviolet, Microwave, X-Rays, and Gamma-Ray frequencies. Conceptual
Physics Pages 408 in addition to your notes.
18) An outpost in deep space receives a signal from Earth in the not so distant future. If the electromagnetic signal
took 5x109 seconds to span the distance from the Earth to the station, how far away is it?
V 
d
t
t *V 
d
*t
t
d  v *t
d  (3.0 *108 m s ) * (5x109 s)
d  1.5 *1018 m
19) What direction will a wave refract when it passes through a boundary from a less dense to a more dense
medium? Low density to High density; Towards the Normal
20) What direction will a wave refract when it passes from a more dense medium to a less dense medium? High
density to Low density; Away from the Normal
21) What specific detail about the wave is changing when is changes media? Its speed is changing
22) A yellow light is shone on a curved mirror at an incident angle of 77o, what is the resultant angle of reflection?
LAW of REFLECTION: Incident angle = reflected angle. Reflected angle is 77o
23) Considering your answer from problem 34, does the angle of reflection change if the surface of the mirror is
irregular or curved? No, the Law of Reflection applies to all surfaces.
F
24) What kind of mirror is indicated above? Concave
25) If light rays are incident through the Focal point, how will they be reflected off of the mirror? Parallel to the
Principal Axis
26) If incident light rays are parallel to the principal axis how will they be reflected off of the mirror? Through the
focal point
27) Does the mirror above cause light rays to diverge or converge? Converge
F
28) What kind of mirror is indicated above? Convex
29) If incident light rays are parallel to the principal axis how will they be reflected?Away from the Principal Axis
30) If light rays are incident through the Focal point, how will they be reflected off of the mirror?
Away from the Principal Axis
31) Does the mirror cause light rays to diverge or converge? Diverge
32) What kind of lens is indicated above? Concave
33) A convex (converging) lens is used in an experiment. The scientist needs to determine the focal length of the
lens in order to verify that her results are valid. If a clear, focused image is projected on a screen at a distance of
12 cm and the light source on the other side of the lens is at a distance of 7cm, what is the focal length of the
1
1
1


lens? Use the Lens Equation:
focal length = 4.4cm
f do di
34) What is the focal length of a lens if the light source is 15cm away from the lens and an image is projected 15cm
on the other side of the lens? Use the Lens Equation: focal length (f) = 7.5cm
35) If the focal length of a lens is 5cm away from the lens and an image is projected 15cm on the other side of the
lens, how far away is the object? Use the Lens Equation: do = 7.5cm
36) An electron is trapped such that it orbits a single, large, positively charged body. The electrostatic force between
the two bodies is F0. If the distance between the charges is quadrupled, by how much does the electrostatic force
change? F0 between the charged bodies would become 1/16 of its original value (Inverse Square law)
37) An electron orbits a positively charged nucleus. The electrostatic force between the two bodies is F0. If the
distance between the charges is cut in half, how does the electrostatic force change? F0 would quadruple
(Inverse Square Law)
38) What is the magnitude of the electrostatic force between a charge of 60.0 C and a charge of 17.00 C if the
charges are separated by a distance of 0.5 m?
Must convert C to C:  = micro = *10-6 >> 60.0 C = 60.0*10-6C = 6.00*10-5 C
17.00 C = 17.00*10-6C = 1.700*10-5 C
q *q
Fe  k e 1 2 2
r
Fe  (8.99 *10 N
9
m2
(6.00 *10 -5 C) * (1.700 *10 -5 C)
Fe  3.668 *101 N
)
C2
2
(0.5m)
Fe  40 N
39) What is the magnitude of the electrostatic force between a charge of 30.0 mC and a charge of 12.00 C if the
charges are separated by a distance of 1.0 m?
Fe  k e
q1 * q2
r2
Fe  (8.99 *10 9 N m
2
C
2
)
(3.00 *10 -2 C) * (1.200 *10 -5 C)
Fe  3.2 *10 3 N
(1.0m) 2
40) What is the distance between a charge of 10.0 C and a charge of 25.00 C if the charges experience a force of
100N?
41) Why does a balloon become negatively charged when it is rubbed by rabbit fur? Electrons are transferred
from the fur to the balloon (Charging by friction).
42) Why does it then stick to a wall if placed against one? The balloon is polarized, by bringing it in proximity
to the wall it will polarize a part of the wall (Temporary charging by induction or polarization).
43) Construct a diagram containing the electric field lines for a positive and a negative electric charge. Label each
electric charge and indicate the direction of each electric field line. Conceptual Physics Pages 519 and 520.
44) Two charged parallel plates in a large field 1000 meters apart captures a lightning bolt. The electric field
intensity between the two charged parallel plates is 7.25 x 106 N/C, what is the potential difference (voltage)
between the plates? V  Ed V  (7.25 *10 6 N / C ) *1x10 3 m V  7.25 x10 9 V V  7 x10 9 V
45) The electric field intensity between two charged parallel plates is 3.3 x 103 N/C, what is the potential difference
(voltage) between the plates if the distance between the plates is 1x10-3 meters?
V  Ed C  (3.3 *10 3 N / C ) *1x10 3 m V  3.3V V  3V
46) Two charged plates are separated by a distance of 3m. If the Voltage across them is 1000V, what is the electric
field intensity between them?
47) Define the photoelectric effect. Photosensitive materials emit electrons after absorbing electromagnetic
radiation.
48) Does it support light as a quantized particle or as a wave? The photoelectric effect is explained by the wave
theory of light.
49) What is the value for Planck’s constant? h=6.63x10-34 Js
50) What is the frequency of a photon with an energy 9.00x10-22 J? E = hf f = E/h f=1.36x1012 Hz
51) What is the energy of a photon with a frequency of 2.0x108 Hz? E = hf
E = 1.3x10-25J
52) What is the energy of a photon with a frequency of 4x1010 Hz? E = hf E = 3x10-23J
53) A power supply gives 5V to a series circuit. If the circuit is carrying 2A of current, what is the value of the
single resistor in the circuit? V=IR R=2.5 Ω
54) A series circuit consists of a 10.V power source and three lamps, RA= 3.0, RB= 1.0, and RC= 2.0.
Determine RT. RT=R1+R2+R3…Rn
RT= 3 + 1 + 2
RT= 6.0
55) Using the information and answer from problem #66 find the current flowing through RC. V=IRT I=V/RT
I=1.7A
56) Using the information and answer from problem #66&67 determine the voltage drop across RA. VA=IRA
VA=5.1V
57) A series circuit consists of a 110.V power source and three lamps, RA= 30.0, RB= 170., and RC= 200..
Find the current flowing through resistor B. RT=R1+R2+R3…Rn
RT= 30.0 + 170. + 200.
V
RT=400.
V=IR I= /R I=0.275A
58) Using the information from problem #68 and your answer for #68, determine the voltage drop across RA.
VA=IRA VA=8.25V
59) What is the equivalent resistance of the circuit in the figure above? RT 
RT 
1
1
1

R1 R2
RT 
1
1
1

20 115
RT 
1
0.05  0.008696
RT 
1
0.059
1
1
1
1
1


 ...
R1 R2 R3
Rn
RT 
1
0.059
RT  17
60) A parallel circuit has a 10V power supply and three resistors in parallel, RA= 3.0, RB= 7.0, and RC= 20..
Determine RT for the circuit. Using equation from #71 RT=1.9
61) A parallel circuit has a 15V power supply and three resistors in parallel, RA= 30.0, RB= 10.0, and RC=
15.0. Determine RT for the circuit. Using equation from #71 RT=5.00
62) How is a voltmeter connected to a circuit to measure voltage? What about an ammeter? Voltmeters are
connected in parallel and Ammeters are connected in series.
V
A
63) Using the schematic diagram above as a baseline, redraw the circuit with a voltmeter measuring voltage across
the 115Ohm resistor, and an ammeter measuring current through the 20Ohm resistor.
64) From the figure above: Object 2 is orbiting object 1 currently at a distance of 1x108 meters. Object 1’s mass is
1x1020 kg and the mass of object two is 1x1010 kg. What is the force of gravity between the two objects at this
point in time?
m *m
(1 *10 20 kg) * (1 *10 20 kg)
FG  7 *10 3 N
FG  G 1 2 2 FG  (6.67 *10 11 Nm 2 / kg 2 )
(1 *108 m) 2
r
65) A balloon flies around the room because _______. Newton’s third law dictates that every action force (air
rushing out of the nozzle) has an equal and opposite reaction force (balloon moving around the room).
66) What is the mass of an object that weighs 196 Newtons?
196 N
Weight
Weight  mg m 
m
m = 20.0kg
m
g
9.81 2
s
67) Consider the diagram above. A small object, attached to a string, is being swung in a circle. If the string were to
break toward what point would the object travel? Draw the answer as a diagram and answer the question as a
text description. The object would fly in a direction tangent to the original circular path.
68) The centrifugal force acting on the mass is being directed toward what point? By definition the centrifugal force
is directed outward (outward seeking), 180 degrees in relation to Centripetal force.
69) Two objects of equal mass are at a fixed distance apart. If the masses of each object could be doubled, the new
gravitational force between the objects would ___________.
FG  m1 * m2 Force of gravity is proportional to mass. FG would increase by a factor of 4.
70) The force of gravity on a 1kg object at the surface of a planet in another solar system is 24 N. What is the force
of gravity on the same object if it were four times farther away from the planet’s surface?
1
FG  2 Force of gravity decreases with the square of the distance. FG would become 24N (1/16) = 1.5N .
r
71) Why do astronauts float inside of the international space station as it orbits the Earth? Both the station and the
astronauts are in freefall, which means they are accelerating at the same rate. With equal accelerations no
support force is possible.
72) How does the International Space Station or any other object in the universe orbit other objects? In other words
what must be happening in order for the object to both remain in orbit and not crash into the Earth even if it is
considered to be in freefall? The Earth’s surface curves away from the freefalling space station. The space
station thus avoids an abrupt end to its perpetual freefall.
73) How are machines subject to the law of conservation of energy? Work output cannot exceed work input.
74) What is the efficiency of a machine that requires 500J of input energy to lift a mass of 10kg to a height of 2
meters?
m
10kg * (9.81 2 ) * 2m
usefulworkoutput
s
*100 efficiency  40%
efficiency 
*100 efficiency 
500 J
workinput
75) A space heater sits in the middle of the room. If you stand in front of it you feel more heat than if you stood
behind it. By what method is energy being transferred from the heater to you? Radiation
76) Two objects of equal masses are a fixed distance apart. If the distance between the two objects could be
increased by a factor of 6, the new gravitational force between the objects would be ________.
1
Fe  2 Force of gravity decreases with the square of the distance. Thus, 62 = 36. FG would become 1/36th .
r
77) Draw a diagram that correctly illustrates the shape and direction of a magnetic field around a bar magnet.
Conceptual Physics Pages 564 and 565 in addition to your notes.
78) Draw a complete picture of an electromagnet (include a correctly orientated power source). Label the poles and
indicate direction of current and magnetic field. Conceptual Physics Pages 577 and 578 in addition to your
notes. Your notes should have the best example.
79) The velocity of electrons in an electron beam is 1.7 x 105 m/s, perpendicular to a magnetic field of 4.3 x 10-2 T.
If the charge on each electron is -1.6 x 10-19 C, what is the magnitude of the force acting on each individual
electron in the beam? F=Bqv F=1.2x10-15 N
80) The velocity of particle in a beam is 2.6 x 106 m/s, perpendicular to a magnetic field of 4.3 x 10-2 T. If the force
experienced by each particle is 1.0N, what is the magnitude of the charge on each particle? F=Bqv
F=1.2x10-15 N
81) A wire carrying 2A of current lays perpendicular to the direction of a magnetic field of 2T intensity. If the wire
is 4m long, what is the force acting on the wire? F=BIL F=16N
82) A pot of water is put on a stove. What method of energy transfer is moving energy from the burner to the pot?
Conduction
83) If spaghetti is placed in the boiling water what method of energy transfer is moving energy from the pot to the
spaghetti? Convection
84) A wire carrying 6mA of current lays perpendicular to the direction of a magnetic field of 2uT intensity. If the
wire is 4cm long, what is the force acting on the wire?
Convert knowns into appropriate units: 6mA = 6*10-3 A
Fe  (2 *10 6 T ) * (6 *10 3 A) * (4 *10 2 m)
Fe  BIL
; 2uT = 2*10-6 T
;
4cm = 4*10-2 m
Fe  4.8 * 10 10 N Fe  5 * 10 10 N
85) Diagram the electrical field lines around - and between – a positive and negative charge of equal strength.
Conceptual Physics Pages 519 and 520.
86) Diagram the electrical field lines around - and between – two like charges of equal intensity. Conceptual
Physics Pages 519 and 520.
87) I to the right, B up the page, what direction is F?
88)
Out of the page
N
S
I
F = ? + (Into the page) ; B=? Down the Page
89) S
N
I +
F = ? From left to Right ; B=? Up the Page