Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) A block of mass m = 4.4 kg, moving on frictionless surface with a speed v = 9.2m / s makes a
1) _____
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sudden perfectly elastic collision with a second block of mass M, as shown in the figure. The
second block is originally at rest. Just after the collision, the 4.4-kg block recoils with a speed of
v f = 2.5m / s What is the mass M of the second block?
A) 3.5 kg
B) 2.4 kg
C) 3.0 kg
D) 7.7 kg
E) 6.7 kg
2) A block of mass m = 3.6 kg, moving on a frictionless surface with a speed v = 9.3m / s makes a
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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 v f = 2.7m / s What is the speed V of
2) _____
the other block?
A) 9.3 m/s
B) 12.0 m/s
C) 6.6 m/s
D) 10.7 m/s
E) 8.0 m/s
3) A 320-g air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary 270-g
cart. What is the speed of the 270-g cart just after the collision?
A) 0.106 m/s
B) 1.14 m/s
C) 0.678 m/s
D) 1.36 m/s
E) 2.72 m/s
3) _____
4) A 320-g air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary 270-g
cart. What is the speed of the 320-g cart just after the collision?
A) 0.68 m/s
B) 0.11 m/s
C) 1.1 m/s
D) 1.4 m/s
E) 0.21 m/s
4) _____
5) A 340-g air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary 300-g
cart. What is the speed of the 300-g cart just after the collision?
A) 1.25 m/s
B) 0.0781 m/s
C) 0.625 m/s
D) 0.664 m/s
E) 1.33 m/s
5) _____
6) A proton of mass m is at rest when it is suddenly struck head-on by an alpha particle (which
consists of 2 protons and 2 neutrons) moving at speed v. If the collision is perfectly elastic, what
speed will the alpha particle have after the collision? (Assume the neutron's mass is equal to the
proton's mass.)
A) 5v/3
B) zero
C) 3v/5
D) 2v/3
6) _____
7) A 50-g ball moving at 10 m/s in the +x direction suddenly collides head-on with a stationary ball
of mass 100 g. If the collision is perfectly elastic, what is the velocity of each ball immediately
after the collision?
A) -3.3 m/s, +6.7 m/s
B) +6.7 m/s, -3.3 m/s
C) -6.7 m/s, +3.3 m/s
D) +3.3 m/s, -6.7 m/s
7) _____
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
8) In a perfectly elastic collision, a 400-g ball moving toward the east at 3.7 m/s suddenly
8) __________
collides head-on with a 200 g ball sitting at rest.
1.2 m/s east
(a) Determine the velocity of the first ball just after the collision.
1.2 m/s east
(b) Determine the velocity of the second ball just after the collision.
1.2 m/s east
(c) Is kinetic energy conserved in this collision? How do you know?
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
9) A 0.140-kg baseball is dropped from rest from a height of 2.20 m above the ground and
9) _____
experiences negligible air resistance as it falls. It rebounds to a height of 1.60 m. What change in
the ball's momentum occurs as it rebounds from the ground?
A) 0.117 kg · m/s upwards
B) 0.350 kg · m/s upwards
C) 0.350 kg · m/s downwards
D) 0.117 kg · m/s downwards
E) 1.70 kg · m/s upwards
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
10) A 0.32-kg ball is moving horizontally at 30 m/s just before suddenly bouncing off a wall
10) __________
Just after the bounce, it is moving horizontally at 25 m/s but in the opposite direction.
(a) What is the magnitude of the change in momentum of the ball during the bounce?
(b) What percentage of the ball's original kinetic energy was lost in the collision?
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
11) In a police ballistics test, a 2.00-g bullet suddenly hits and becomes embedded in a 5.00-kg wood
11) _____
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 the block?
A) 789 m/s
B) 16.7 m/s
C) 262 m/s
D) 25.3 m/s
E) 524 m/s
12) A block of mass m = 9.0 kg and speed V and is behind a block of mass M = 27 kg and speed of
0.50m / s as shown int 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. How much kinetic
energy of the blocks is lost due to the collision?
A) 8.6 J
B) 2.0 J
C) 31 J
D) 4.6 J
E) 11 J
13) 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 of the string is 2.0 m. What
was the speed of the bullet just before it struck the wooden block?
A) 250 m/s
B) 420 m/s
C) 67 m/s
D) 370 m/s
What was the initial speed v of the bullet?
13) _____
E) 650 m/s
14) 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 constant (spring constant) of the spring
is
12) _____
14) _____
A) 500 m/s
B) 480 m/s
C) 520 m/s
D) 460 m/s
E) 440 m/s
An 8.0-g bullet is suddenly shot into a 4.0-kg block, 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 8.9 cm. The force constant (spring constant) of the spring is
15) _____
What is the magnitude of the impulse on the block (including the bullet inside) due
to the spring during the entire time interval during which the block compresses the spring?
15)
A) 10 N · s
B) 12 N · s
C) 6.7 N · s
D) 13 N · s
E) 8.3 N · s
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
16) In a police rifle test, a 15-g bullet traveling 213 m/s in a vertical direction suddenly
16) __________
buries itself in a 2.4-kg block of wood at rest directly above it. As a result, the bulletblock combination moves vertically upward.
1.3 m/s
(a) Determine the velocity of the bullet-block combination just after the impact.
0.089m
(b) Determine the maximum height reached by the bullet/block combination.
Inelastic collision
(c) Is kinetic energy conserved in this collision?
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
17) In a certain nuclear reactor, neutrons suddenly collide with deuterons, which have twice the
17) _____
mass of neutrons. In a head-on elastic collision with a stationary deuteron, what fraction of the
initial kinetic energy of a neutron is transferred to the deuteron?
A) 3/4
B) 8/9
C) 1/3
D) 1/2
E) 5/6
18) In a certain nuclear reactor, neutrons suddenly collide with carbon nuclei, which have 12 times
the mass of neutrons. In a head-on elastic collision with a stationary carbon nucleus, what
fraction of its initial speed does the neutron have after the collision?
A) 10/13
B) 11/12
C) 1/12
D) 11/13
E) 5/6
18) _____
19) An object initially at rest suddenly explodes in two fragments of masses
19) _____
move in opposite directions. If the speed of the first fragment is
of the explosion.
A) 38 J
B) 38 kJ
C) 30 J
and
that
find the internal energy
D) 30 kJ
20) Two simple pendulums of equal length l = 0.45 m are suspended from the same point. The
pendulum bobs are small solid steel spheres. The first bob is drawn back to make a 35° angle
with the vertical, while the other one is left hanging at rest. If the first bob has a mass of 0.25 kg
20) _____
and the second has a mass of
how high will the second bob rise above its initial position
when struck elastically by the first bob after it is released?
A) 4.4 cm
B) 2.7 cm
C) 3.9 cm
D) 3.3 cm
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
21) On a frictionless horizontal surface, a 1.50-kg mass traveling at 3.50 m/s suddenly
21) __________
collides with and sticks to a 3.00-kg mass that is initially at rest, as shown in the figure.
This system then runs into an ideal spring of force constant (spring constant) 50.0 N/cm.
(a) What will be the maximum compression distance of the spring?
(b) How much mechanical energy is lost during this process? During which parts of the 3.5 cm
process (the collision and compression of the spring) is this energy lost? 6.13 J, lost during inelastic collisions
22)
A baseball pitcher is employing a ballistic pendulum to determine the speed of his
22) __________
fastball. A
lump of clay is suspended from a cord 2.0 m long. When the pitcher
throws his fastball aimed directly at the clay, the ball suddenly becomes embedded in
the clay and the two swing up to a maximum height of 0.080 m. If the mass of the
21 m/s
baseball is 0.21 kg, find the speed of the pitched ball.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
23) A 1200-kg pick-up truck traveling south at 15 m/s suddenly collides with a 750-kg car that is
23) _____
traveling east. The two vehicles stick together and slide along the road after colliding. A
highway patrol officer investigating the accident determines that the final position of the
wreckage after the collision is 25 m, at an angle of 50° south of east, from the point of impact. She
also determines that the coefficient of kinetic friction between the tires and the road at that
location was 0.40. What was the speed of the car just before the collision?
A) 17 m/s
B) 20 m/s
C) 4.8 m/s
D) 23 m/s
E) 14 m/s
24) A uniform solid cylinder with a radius of 10 cm and a mass of 3.0 kg is rotating about its center
with an angular speed of 33.4 rpm. What is its kinetic energy?
A) 0.96 J
B) 0.18 J
C) 1.1 J
D) 17 J
E) 0.092 J
24) _____