physics study guide 3 doss

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you.
You have two choices about what to do with the ball: either catch the ball or deflect it back toward
your friend with the same speed as it was originally t

B) Deflect the ball back.

Two air track carts move along an air track towards each other. Cart A has a mass of 450 g and
moves toward the right with a speed of 0.850 m/s. Cart B has a mass of 300 g and moves toward the
left with a speed of 1.12 m/s. What is the total momentum of t

A) 0.047 kg � m/s toward the right

Two astronauts, of masses 60 kg and 80 kg, are initially right next to each other and at rest in
outer space. They suddenly push each other apart. How far has the heavier astronaut moved when
the lighter astronaut has moved 12 m?
A) 16 m B) 9.0 m C) 21 m

B) 9.0 m

A 0.140-kg baseball is thrown with a velocity of 27.1 m/s. It is struck by the bat with an average
force of 5000 N, which results in a velocity of 37.0 m/s in the opposite direction from the original
velocity. How long were the bat and ball in contact?
A)

A) 1.79 x 10^-3 s

A girl of mass 55 kg throws a ball of mass 0.80 kg against a wall. The ball strikes the wall
horizontally with a speed of 25 m/s, and it bounces back with this same speed. The ball is in contact
with the wall .050 s. What is the magnitude of the average f

A) 800 N

A 0.24 kg blob of clay is thrown at a wall with an initial horizontal velocity of If the clay
comes to a stop in what is the average horizontal force on the clay due to the wall?
A) 42 N B) 26 N C) 35 N D) 51 N

A) 42 N

A block of mass m = 34 kg and speed V is behind a block of mass M = 81 kg and speed of
as shown in the figure. The surface is frictionless and the blocks collide and couple. After the
collision, the blocks have a common speed of What is the magnitude of t

C) 32 N s

A very small 51-g steel ball is released from rest and falls vertically onto a steel plate. The ball
strikes the plate and is in contact with it for 0.50 ms. The ball rebounds elastically and returns to its
original height. The total time interval for a r

D) 3000 N

A 0.140-kg baseball is dropped from rest. It has a speed of 1.20 m/s just before it hits the ground,
and it rebounds with an upward speed of 1.00 m/s. The ball is in contact with the ground for 0.0140
s. What is the average force exerted by the ground on

C) 22.0 N upwards

A block of mass m = 5.6 kg, moving on a frictionless surface with a velocity of to the
right, collides with a block of mass M at rest, as shown in the figure. After the collision, the 5.6-kg
block recoils with a velocity of to the left. If the blocks are

A) 202 N

A block of mass m = 3.6 kg, moving on a frictionless surface with a speed makes a
sudden perfectly elastic collision with a stationary block of mass M, as shown in the figure. Just after
the collision, the 3.6-kg block recoils with a speed of What is the

A) 6.6 m/s

A 0.340-kg air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary
0.3300-kg cart. What is the speed of the 0.300-kg cart just after the collision?
A)
0.0781
m/s
B)
1.33
m/s
C)
0.625
m/s
D)
1.25
m/s
E)
0.664
m/s

B) 1.33 m/s

In a police ballistics test, a 2.00-g bullet suddenly hits and becomes embedded in a 5.00-kg wood
block which is hanging from a 1.20-m long string. This causes the block to swing through an arc of
3.50�. What was the speed of the bullet just before it hit

D) 524 m/s

A block of mass m = 9.0 kg and speed V and is behind a block of mass M = 27 kg and speed of
as shown in the figure. The surface is frictionless, and the blocks suddenly collide and
couple. After the collision, the blocks have a common speed of 0.90 m/s. H

C) 8.6 J

As shown in the figure, a bullet of mass 0.010 kg moving horizontally suddenly strikes a block of
wood of mass 1.5 kg that is suspended as a pendulum. The bullet lodges in the wood, and together
they swing upward a vertical distance of 0.40 m. The length

D) 420 m/s

An 8.0-g bullet is suddenly shot into a 4.0-kg block that is at rest on a frictionless horizontal
surface, as shown in the figure. The bullet remains lodged in the block. The block then moves
against a spring and compresses it by 3.7 cm. The force constan

B) 460 m/s

A merry-go-round spins freely when Diego moves quickly to the center along a radius of the
merry-go-round. As he does this, it is true to say that
A) the moment of inertia of the system decreases and the angular speed increases.
B) the moment of inertia o

A) the moment of inertia of the system decreases and the angular speed increases

At a certain instant, a compact disc is rotating at 210 rpm. What is its angular speed in rad/s?
A) 11 rad/s B) 22 rad/s C) 45 rad/s D) 69 rad/s E) 660 rad/s

B) 22 rad/s

When a fan is turned off, its angular speed decreases from 10 rad/s to 6.3 rad/s in 5.0 s. What is
the magnitude of the average angular acceleration of the fan?
A) 0.86 rad/s2 B) 0.74 rad/s2 C) 0.37 rad/s2 D) 11 rad/s2 E) 1.2 rad/s2

B) 0.74 rad/s^2

A child is riding a merry-go-round that is turning at 7.18 rpm. If the child is standing 4.65 m
from the center of the merry-go-round, how fast is the child moving?
A) 0.556 m/s B) 1.75 m/s C) 1.80 m/s D) 3.50 m/s E) 5.64 m/s

D) 3.50 m/s

What is the kinetic energy of a 120-cm thin uniform rod with a mass of 450 g that is rotating
about its center at 3.60 rad/s?
A) 0.350 J B) 4.20 J C) 0.700 J D) 0.960 J E) 2.10 J

A) 0.350 J

A solid uniform sphere of mass 120 kg and radius 1.7 m starts from rest and rolls without
slipping down an inclined plane of vertical height 5.3 m. What is the angular speed of the sphere at
the bottom of the inclined plane?
A) 5.1 rad/s B) 8.7 rad/s C) 9

A) 5.1 rad/s

A solid uniform disk of diameter 3.20 m and mass 42 kg rolls without slipping to the bottom of a
hill, starting from rest. If the angular speed of the disk is 4.27 rad/s at the bottom, how high did it
start on the hill?
A) 2.68 m B) 3.14 m C) 3.57 m D) 4.

C) 3.57 m

A wheel having a moment of inertia of 5.00 kg � m2 starts from rest and accelerates under a
constant torque of 3.00 N � m for 8.00 s. What is the wheel's rotational kinetic energy at the end of
8.00 s?
A) 57.6 J B) 64.0 J C) 78.8 J D) 122 J

A) 57.6 J

A man in a gym is holding an 8.0-kg weight at arm's length, a distance of 0.55 m from his
shoulder joint. What is the torque about his shoulder joint due to the weight if his arm is horizontal?
A) 0.24 N � m B) 4.4 N � m C) 15 N � m D) 43 N � m E) 0 N � m

D) 43 N m

A mechanic is examining the wheel of a bicycle to adjust the brake. With the bicycle off the
ground, he manually rotates the wheel until it reaches an angular speed of 12.0 rad/s and then allows
it to coast to a stop. If the wheel has a moment of inertia

B) 0.00750 N m

A light-weight potter's wheel, having a moment of inertia of is spinning freely at 40.0
rpm. The potter drops a small but dense lump of clay onto the wheel, where it sticks a distance 1.2 m
from the rotational axis. If the subsequent angular speed of the

A) 4.2 kg

A 40.0-kg child running at 3.00 m/s suddenly jumps onto a stationary playground merry-goround
at a distance 1.50 m from the axis of rotation of the merry-go-round. The child is traveling
tangential to the edge of the merry-go-round just before jumping on.

B) 0.261 rad/s

If the sum of the external forces on an object is zero, then the sum of the external torques on it
must also be zero.
A) True B) False

B) False

If the sum of the external torques on an object is zero, then the sum of the external forces on it
must also be zero.
A) True B) False

B) False

If the sum of both the external torques and the external forces on an object is zero, then the
object must be at rest.
A) True B) False

B) False

A 15-kg child is sitting on a playground teeter-totter, 1.5 m from the pivot. What is the
magnitude of the minimum force, applied 0.30 m on the other side of the pivot, that is needed to
make the child lift off the ground?
A) 740 N B) 75 N C) 66 N D) 44 N

A) 740 N

An athlete holds a 7.5-kg shot put in his hand with his lower arm horizontal, as shown in the
figure. His lower arm has a mass of 2.8 kg and its center of gravity (or center of mass) is 12 cm from
the elbow-joint pivot. How much force must the extensor mu

C) 1000 N

A store's sign has a mass of 20 kg and is 3.0 m long. It is
uniform, so its center of gravity is at the center of the sign. It is supported horizontally by a small
loose bolt attached to the wall at one end and by a wire at the other end, as shown in the

C) 230 N

In the figure, a uniform ladder of weight 200 N and length 10 m leans against a perfectly smooth
wall. A firefighter of weight 600 N climbs a distance x up the ladder. The coefficient of static
friction between the ladder and the floor is 0.50. What is th

D) 6.3 m

A cable is 100-m long and has a cross-sectional area of 1.0 mm2. A 1000-N force is applied to
stretch the cable. Young's modulus for the cable is 1.0 � 1011 N/m2. How far does the cable
stretch?
A) 0.010 m B) 0.10 m C) 1.0 m D) 10 m

C) 1.0 m

A solid steel column is 4.0 m long and 0.20 m in diameter. Young's modulus for this steel is
2.0 � 1011 N/m2. By what distance does the column shrink when a 5000-kg truck is supported by
it?
A) 8.0 � 10-7 m B) 3.2 � 10-6 m C) 7.8 � 10-6 m D) 3.1 � 10-5 m

D) 3.1 x 10^-5 m

A vertical 30-cm steel rod, 1.0 cm in diameter, supports a 300-kg mass. What is the change in
length of the rod caused by this mass? Young's modulus for steel is 2.0 � 1011 N/m2.
A) 5.6 � 10-5 m B) 6.5 � 10-5 m C) 5.6 � 10-6 m D) 6.5 � 10-6 m E) 6.5 � 10-

A) 5.6 x 10^-5 m

A 5000-N force compresses a steel block by 0.0025 cm. How much force, applied over the same
area, would be needed to compress the block by 0.0125 cm?
A) 1,000 N B) 2,500 N C) 5,000 N D) 25,000 N

D) 25,000 N

A 12-L volume of oil is subjected to pressure which produces a volume strain of -3.0 � 10-4.
The bulk modulus of the oil is 6.0 � 109 Pa and is independent of the pressure. The change in the
pressure of the oil in megapascals is closest to
A) 1.2 MPa. B)

D) 1.8 MPa