Download PHY 131–003 - Oakton Community College

PHY 131–003
Oakton Community College
Spring 2010
Practice Test 2
Useful formulas:
v
x
t
a
v
t

A  A  Ax 2  Ay 2  Az 2

A  Ax xˆ  A y yˆ  Az zˆ
Constant acceleration:
vx = v0x + axt
x  x 0  v x t  12 a x t 2



Relative motion: rP|E  rP|A  rA|E



v P|E  v P|A  v A|E


Fnet  ma
w = mg
a rad 
Ffriction = µFnormal
v2
R
Fg  
Gm1m2
r
Fspring = –kx
PEgrav = mgh
PEspring 
vx2 = v0x2 + 2ax(x – x0)
g = 9.80 m/s2
KE 
1 2
kx
2
1
mv 2
2
P
m r

m

rCM


Mv CM  P
i
i
RE 2
W
t


p  mv


p
Fnet 
t
Elastic collisions: vA – vB = v’B – v’A

i i
Gm E
W = KE2 – KE1
KE1 + PEgrav, 1 + PEspring, 1 = KE2 + PEgrav, 2 + PEspring, 2 + heat
mAvA + mBvB = mAv’A + mBv’B
g
G = 6.673 × 10–11 Nm2/kg2
2
W = Fd
 Ay 
  180 

 Ax 
  arctan




P
Fext Ma CM 
t
i
 av, z 

t
 av,z 
 z
t
Constant angular acceleration:
s = r
v = r
a tan 
 z   0 z   z t    0   0 z t  12  z t 2
dv d (r )
d

r
 r
dt
dt
dt
a rad 
 z 2   0 z 2  2    0 
v2
  2r
r
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PHY 131–003
Oakton Community College
Spring 2010
Practice Test 2
Useful formulas:
I
m r
2
i i
K rot  12 I 2
IP = ICM + Md2
i


Torque:   Fl  rF sin   Ftan r
z
 I z
K  K trans  K rot 
1
1
mv cm 2  I cm  2
2
2
Rolling without slipping: vcm = R 
2


W   z d
For constant torque: W = z
1
L = mvr

L

t
L = I
Wrot  K rot 


1
1
I 2 2  I12
2
2
P = z z
Precession:  
wr
I
1 m = 109 nm
1 g/cm3 = 1000 kg/m3
 



Apparent weight: w  w 0  ma rad  mg 0  ma rad
Conversion factors:
100 cm = 1 m
1 km = 1000 m
1 m3 = 1000 L = 106 cm3 1 Pa = 1 N/m2
2 rad = 360°
 rad = 180°
The Sun: mS = 1.99 × 1030 kg
The Earth: mE = 5.97 × 1024 kg
RE = 6.38 × 106 m
rE = 1.50 × 1011 m
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PHY 131–003
Oakton Community College
Spring 2010
Practice Test 2
1) An electron, whose mass is 9.11 × 10–31 kg, has a constant speed of 1.00 × 108 m/s. A magnetic field
causes the electron to travel in a circular path of radius 1.00 cm without losing any speed. What is the
magnitude of the force that the magnetic field exerts on the electron?
2) Conical pendulum: A pendulum made by placing a 0.250 kg ball at the end of a 1.00m massless cord
swings in a conical path. The ball traces out a circle in a horizontal plane while maintaining the same
height. If the cord maintains a 30° angle with the vertical, what is the speed of the ball?
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PHY 131–003
Oakton Community College
Spring 2010
Practice Test 2
3) Given that the radius of mars is 0.533 times that of earth, and its mass is 0.108 times that of earth:
a) How much would a person weigh on mars if that person weighs 800.0 N on earth? b) If you could
change the radius of mars without changing its mass, what radius would it have to have for this person's
weight on mars to be the same as it is on earth?
4) A factory worker pushes a crate of mass 40.0 kg across the floor a distance of 10.0 m at a constant
velocity using a horizontal force of 75.0 N. a) How much work is done on the crate by the worker? b) How
much work is done on the crate by the floor?
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PHY 131–003
Oakton Community College
Spring 2010
Practice Test 2
5) A car on a frictionless horizontal track has a mass of 0.250 kg. It is connected to a spring and held at a
position where the spring is compressed by 0.100 m. The force constant of the spring is 6.25 N/m.
Assuming there is no friction, what is the speed of the car when the spring is at its uncompressed length
(x = 0.0 m)?
6) A ball of mass 0.40 kg moves horizontally at a velocity of 25.0 m/s. It bounces off of a wall and it has a
velocity of 18.0 m/s in the opposite direction. The ball was in contact with the wall for 0.015 s. What was
the average force exerted on the ball by the wall?
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PHY 131–003
Oakton Community College
Spring 2010
Practice Test 2
7) On a frictionless track, car A, with mass mA = 0.300 kg, moves to the right toward car B with velocity
vA = +2.00 m/s. Car B, with mass mB = 0.250 kg, moves toward car A with a velocity of
vB = –1.50 m/s. After the collision, car B has a velocity of v’B = +1.50 m/s. a) What is the velocity of car A
after the collision, v’A? b) What is the change in the kinetic energy of this two-car system?
8) A DVD disk is spinning at an angular velocity of 27.5 rad/s, then it experiences a constant angular
acceleration of –10.0 rad/s2 until the disk comes to rest. Through how many revolutions did the disk turn
during its deceleration?
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PHY 131–003
Oakton Community College
Spring 2010
Practice Test 2
9) For the disk of problem 8, point A lies 59 mm from the center of the disk. a) What was the tangential
speed of point A before the deceleration? b)What was its tangential acceleration during the deceleration?
10) A massless rope is wrapped around a 36.0 kg cylindrical drum, initially at rest. The radius of the drum
is 0.100 m, and its moment of inertia is: I  12 MR 2 . The rope is pulled, without slipping, with a force of
15.0 N. a) What is the kinetic energy of the drum after the rope has been pulled for 3.00 m? b) What is the
angular velocity of the drum at this time?
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