PHY 141 EXAM 3 CONCEPTUAL
QUESTIONS WITH ACTUAL ANSWERS
Two objects are known to have the same kinetic energy. Do these two objects
necessarily have the same momentum? (Y/N) - Answer No
A system of particles is known to have zero momentum. Does it follow that the kinetic
energy of the system is also zero? (Y/N) - Answer No
A railroad car of mass m and speed collides and sticks to an identical railroad car that is
initially at rest. After the collision, how is the kinetic energy of the system compared to
its initial kinetic energy?
A. 1/2 of its initial
B. 1/3 of its initial
C. 1/4 of its initial
D. the same as its initial - Answer A
Two cars collide at an intersection. If the cars do not stick together, can we conclude
that their collision was elastic? (Y/N) - Answer No
In an inelastic collision, is it possible for objects to lose most of their kinetic energy,
while at the same time losing none of their momentum? (Y/N) - Answer Yes
An iceberg floats in a shallow sea. What can you say about the pressures at points 1
(directly under iceberg) and 2 (same depth as point 1 but not under iceberg)?
A. p1>p2
B. p1=p2
C. p1<p2 - Answer B
What can you say about the pressures at points 1 (in an open container of fluid) and 2
(same depth and container as point 1 but not under open top)?
A. p1>p2
B. p1<p2
C. p2=p1 - Answer C
A heavy lead block and a light aluminum block of equal sizes are both submerged in
water. Upon which is the buoyant force greater?
A. On the lead block
B. On the aluminum block
C. They both experience the same buoyant force - Answer C
, Two blocks are of identical size. One is made of lead and sits on the bottom of a pond;
the other is of wood and floats on top. Upon which is the buoyant force greater?
A. On the lead block
B. On the wood block
C. They both experience the same buoyant force - Answer A
Which floating block is most dense (A has 80% in the water, B has 30% in the water,
and C has 50% in the water)?
A. block a
B. block b
C. block c
D. blocks a and b are same
E. blocks b and c are same - Answer A
Blocks A, B, and C are all the same size. A is 50g and closest to the surface, B is 40g
and midway to the surface, and C is 50g and the deepest. Which experiences the
largest buoyant force?
A. block a
B. block b
C. block c
D. all have the same
E. blocks a and c have the same but block b is different - Answer D
Blocks A, B, and C are all the same size. They are hanging from scales; A is 40g and
2cm deep, B is 40g and 10cm deep, and C is 50g and 2cm deep. Which is the correct
order of the scale readings?
A. a=b=c
B.c>a=b
C. c>a>b
D. b>c>a
E. a=c>b - Answer B
To win a prize at the county fair, you're trying to knock down a bowling pin by hitting it
with a thrown object. Should you choose to throw a rubber ball, which will bounce off the
pin, or a beanbag, which will strike the pin and not bounce? Assume the ball and
beanbag have equal size and weight.
A. rubber ball
B. beanbag
C. it doesnt matter - Answer A
Model rocket engines are rated by their thrust force and by the impulse they provide.
You can use this information to determine the time interval at which the engines fire.
Two rocket engines provide the same impulse. The first engine provides 6 N of thrust
for 2s; the second provides 4N of thrust. For how long does this second engine fire?
A. 1s
QUESTIONS WITH ACTUAL ANSWERS
Two objects are known to have the same kinetic energy. Do these two objects
necessarily have the same momentum? (Y/N) - Answer No
A system of particles is known to have zero momentum. Does it follow that the kinetic
energy of the system is also zero? (Y/N) - Answer No
A railroad car of mass m and speed collides and sticks to an identical railroad car that is
initially at rest. After the collision, how is the kinetic energy of the system compared to
its initial kinetic energy?
A. 1/2 of its initial
B. 1/3 of its initial
C. 1/4 of its initial
D. the same as its initial - Answer A
Two cars collide at an intersection. If the cars do not stick together, can we conclude
that their collision was elastic? (Y/N) - Answer No
In an inelastic collision, is it possible for objects to lose most of their kinetic energy,
while at the same time losing none of their momentum? (Y/N) - Answer Yes
An iceberg floats in a shallow sea. What can you say about the pressures at points 1
(directly under iceberg) and 2 (same depth as point 1 but not under iceberg)?
A. p1>p2
B. p1=p2
C. p1<p2 - Answer B
What can you say about the pressures at points 1 (in an open container of fluid) and 2
(same depth and container as point 1 but not under open top)?
A. p1>p2
B. p1<p2
C. p2=p1 - Answer C
A heavy lead block and a light aluminum block of equal sizes are both submerged in
water. Upon which is the buoyant force greater?
A. On the lead block
B. On the aluminum block
C. They both experience the same buoyant force - Answer C
, Two blocks are of identical size. One is made of lead and sits on the bottom of a pond;
the other is of wood and floats on top. Upon which is the buoyant force greater?
A. On the lead block
B. On the wood block
C. They both experience the same buoyant force - Answer A
Which floating block is most dense (A has 80% in the water, B has 30% in the water,
and C has 50% in the water)?
A. block a
B. block b
C. block c
D. blocks a and b are same
E. blocks b and c are same - Answer A
Blocks A, B, and C are all the same size. A is 50g and closest to the surface, B is 40g
and midway to the surface, and C is 50g and the deepest. Which experiences the
largest buoyant force?
A. block a
B. block b
C. block c
D. all have the same
E. blocks a and c have the same but block b is different - Answer D
Blocks A, B, and C are all the same size. They are hanging from scales; A is 40g and
2cm deep, B is 40g and 10cm deep, and C is 50g and 2cm deep. Which is the correct
order of the scale readings?
A. a=b=c
B.c>a=b
C. c>a>b
D. b>c>a
E. a=c>b - Answer B
To win a prize at the county fair, you're trying to knock down a bowling pin by hitting it
with a thrown object. Should you choose to throw a rubber ball, which will bounce off the
pin, or a beanbag, which will strike the pin and not bounce? Assume the ball and
beanbag have equal size and weight.
A. rubber ball
B. beanbag
C. it doesnt matter - Answer A
Model rocket engines are rated by their thrust force and by the impulse they provide.
You can use this information to determine the time interval at which the engines fire.
Two rocket engines provide the same impulse. The first engine provides 6 N of thrust
for 2s; the second provides 4N of thrust. For how long does this second engine fire?
A. 1s
