Physics C Momentum Concepts Week 1

Question 1
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A railroad car of mass m is moving at speed v when it collides with a second railroad car of mass M which is at rest.   The two cars lock together instantaneously and move along the track.   What is the speed of the cars immediately after the collision?
Select one:
a. mv/M
b. v/2
c. (m + M )v/m
d. Mv/m
e. mv/(m+M) Correct
Question 2
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A billiard ball collides in an elastic head on collision with a second identical ball.  What is the kinetic energy of the system after the collision compared to that before the collision?
Select one:
a. the same Correct
b. twice
c. four times
d. one fourth
Question 3
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
nar004-1.jpg
A block of mass 3 kg, initially at rest, is pulled along a frictionless, horizontal surface with a force shown as a function of time t by the graph above.

The speed of the block in meters per second at t = 2 s is
Select one:
a. 24
b. 4
c. 8/3
d. 8
e. 4/3  Correct
Question 4
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text

mc048-1.jpg
A person is standing at one end of a uniform raft of length L that is floating motionless on water, as shown above.  The center of mass of the person-raft system is distance d from the center of the raft.  The person then walks to the other end of the raft.  If friction between the raft and the water is negligible, how far does the raft move relative to the water?
Select one:
a. mc048-3.jpg
b. d
c. L
d. 2d Correct
e. mc048-2.jpg
Question 5
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
mc005-1.jpg

1.      A ball initially moves horizontally with velocity vi, as shown above. It is then struck by a stick. After leaving the stick, the ball moves vertically with a velocity vf, which is smaller in magnitude than vi.  Which of the following vectors best represents the direction of the average force that the stick exerts on the ball?
mc005-2.jpgmc005-3.jpgmc005-4.jpg
Select one:
a. c
b. d
c. e
d. a
e. b Correct
Question 6
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
nar001-1.jpg
A 4-kilogram mass has a speed of 6 meters per second on a horizontal frictionless surface, as shown above. The mass collides head-on and elastically with an identical 4-kilogram mass initially at rest. The second 4-kilogram mass then collides head-on and sticks to a third 4-kilogram mass initially at rest.

The final speed of the two 4-kilogram masses that stick together is
Select one:
a. 6 m/s
b. 3 m/s Correct
c. 4 m/s
d. 0 m/s
e. 2 m/s
Question 7
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A solid metal ball and a hollow plastic ball of the same external radius are released from rest in a large vacuum chamber. When each has fallen 1m, they both have the same
Select one:
a. speed Correct
b. change in potential energy
c. kinetic energy
d. inertia
e. momentum
Question 8
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
mc012-1.jpg

A piece of wire of uniform cross section is bent in the shape shown above. What are the coordinates  (x, y ) of the center of mass?
Select one:
a. (1,6/7)
b. (6/7, 6/7)
c. (15/14, 8/7)
d. (15/14, 6/7) Correct
e. (1,1)
Question 9
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A person holds a portable fire extinguisher that ejects 1.0 kg of water per second horizontally at a speed of 6.0 m/s.  What horizontal force in newtons must the person exert on the extinguisher in order to prevent it from accelerating?
Select one:
a. 10 N
b. 36 N
c. 0 N
d. 18 N
e. 6 N Correct
Question 10
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
nar002-1.jpg
A system consists of two objects having masses ml and m2 (ml < m2).  The objects are connected by a massless string, hung over a pulley as shown above, and then released.

When the object of mass m2 has descended a distance h, the potential energy of the system has decreased by
Select one:
a. 0
b. ½(ml + m2)gh
c. (m2 - ml)gh  Correct
d. (m1 + m2)gh
e. m2gh
Question 11
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
An object is initially traveling at velocity v.  Suddenly, the object's speed is doubled.  What statement is correct?
Select one:
a. Its momentum remains the same; its kinetic energy doubles
b. Its momentum quadruples; its kinetic energy doubles
c. Its momentum doubles; its kinetic energy doubles
d. Its momentum doubles; its kinetic energy remains the same
e. Its momentum doubles; its kinetic energy quadruples Correct
Question 12
Incorrect
Mark 0.00 out of 1.00
Not flaggedFlag question
Question text
mc046-1.jpg
A uniform square plate of size 6 m on a side has a square piece of size 2 m removed.  The center of the removed piece is at (2m, 0m) as shown above.  The center of the mass of the remaining piece is
Select one:
a. not possible to tell from the given information.
b. on the y axis but below the x axis.
c. on the x axis but to the left of the y axis. Incorrect
d. on the x axis but to the right of the y axis.
e. on the y axis but above the x axis.
Question 13
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A balloon of mass M is floating motionless in the air.  A person of mass less than M is on a rope ladder hanging from the balloon. The person begins to climb the ladder at a uniform speed v relative to the ground. How does the balloon move relative to the ground?
Select one:
a. Down with speed v
b. Up with a speed less than v
c. Down with a speed less than v Correct
d. Up with speed v
e. The balloon does not move.
Question 14
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
mc016-1.jpg
        mc016-2.jpg

The center of mass of a uniform wire, bent in the shape shown above, is located closest to point
Select one:
a. C
b. E
c. D
d. A
e. B Correct
Question 15
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
mc032-1.jpg
A stationary object explodes, breaking into three pieces of masses m, m, and 3m. The two pieces of mass m move off at right angles to each other with the same magnitude of momentum mV, as shown in the diagram above. What are the magnitude and direction of the velocity of the piece having mass 3m ?
          Magnitude            Direction
Select one:
a. mc032-6.jpg                      mc032-7.jpg
b. mc032-8.jpg                       mc032-9.jpg Correct
c. mc032-10.jpg                        mc032-11.jpg
d. mc032-2.jpg                         mc032-3.jpg
e. mc032-4.jpg                         mc032-5.jpg
Question 16
Incorrect
Mark 0.00 out of 1.00
Not flaggedFlag question
Question text
nar001-1.jpg
A 4-kilogram mass has a speed of 6 meters per second on a horizontal frictionless surface, as shown above. The mass collides head-on and elastically with an identical 4-kilogram mass initially at rest. The second 4-kilogram mass then collides head-on and sticks to a third 4-kilogram mass initially at rest.

The final speed of the first 4-kilogram mass is
Select one:
a. 6 m/s
b. 0 m/s
c. 3 m/s Incorrect
d. 2 m/s
e. 4 m/s
Question 17
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
1.      A toy spacecraft is launched directly upward.  When the toy reaches its highest point, a spring is released and the toy splits into two parts with masses of 0.02 kg and 0.08 kg, respectively.  Immediately after the separation, the 0.02 kg part moves horizontally due east.  Air resistance  is negligible.  True statements about the 0.08 kg part include which of the following?
I.      It could move north immediately after the spring is released.
II.      It takes longer to reach the ground than does the 0.02 kg part.
III.      It strikes the ground farther from the launch point than does the 0.02 kg part.
Select one:
a. III only
b. I and II only
c. II and III only
d. None
 Correct
e. I only
Question 18
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
nar002-1.jpg
A system consists of two objects having masses ml and m2 (ml < m2).  The objects are connected by a massless string, hung over a pulley as shown above, and then released.

When the speed of each object is v, the magnitude of the total linear momentum of the system is
Select one:
a. ½(m2 - m1)v
b. ½(ml+m2)v
c. (m2 - m1) v Correct
d. m2v
e. (m1 + m2) v
Question 19
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
mc023-1.jpg

A tennis ball of mass m rebounds from a racquet with the same speed v as it had initially. as shown above. The magnitude of the momentum change of the ball is
Select one:
a. 2mv
b. mv
c. 0
d. 2mvcosq Correct
e. 2mvsinq
Question 20
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A rock is lifted for a certain time by a force F that is greater in magnitude than the rock's weight W. The change in kinetic energy of the rock during this time is equal to the
Select one:
a. work done by W alone
b. difference in the momentum of the rock before and after this time
c. difference in the potential energy of the rock before and after this time
d. work done by F alone
e. work done by the net force (F - W)  Correct
Question 21
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A balloon of mass M is floating motionless in the air.  A person of mass less than M is on a rope ladder hanging from the balloon. The person begins to climb the ladder at a uniform speed v relative to the ground. How does the balloon move relative to the ground?
Select one:
a. Up with speed v
b. Down with a speed less than v Correct
c. The balloon does not move
d. Up with a speed less than v
e. Down with speed v
Question 22
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A rubber ball with a mass of 0.20 kg is dropped onto a steel plate. The ball's speed just before impact is 4.6 m/s and just after impact is 4.4 m/s.  What is the magnitude of the change in the ball's momentum?
Select one:
a. 4.0mc037-5.jpg
b. 2.0 mc037-4.jpg
c. 1.8 mc037-3.jpg Correct
d. 0.20 mc037-2.jpg
e. 0.04 mc037-1.jpg
Question 23
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
nar004-1.jpg
A block of mass 3 kg, initially at rest, is pulled along a frictionless, horizontal surface with a force shown as a function of time t by the graph above.

The acceleration of the block in meters per second squared at t = 2 s is
Select one:
a. 4/3 Correct
b. 2
c. 12
d. 8
e. 3/4
Question 24
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
mc004-1.jpg
An object having an initial momentum that may be represented by the vector above strikes an object that is initially at rest.  Which of the following sets of vectors may represent the momenta of the two objects after the collision?
mc004-2.jpg
Select one:
a. d
b. b
c. a
d. c
e. e Correct
Question 25
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A railroad flatcar of mass 2,000 kilograms rolls to the right at 10 meters per second and collides with a flatcar of mass 3,000 kilograms that is rolling to the left at 5 meters per second.  The flatcars couple together. Their speed after the collision is
Select one:
a. 1 m/s  Correct
b. 7.5 m/s
c. 5 m/s
d. 7 m/s
e. 2.5 m/s
Question 26
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
mc038-1.jpg

A force acts on a body initially at rest for 3 seconds as shown in the accompanying graph.  What is the change in momentum of the object?
Select one:
a. 2 mc038-2.jpg
b. 5 mc038-3.jpg Correct
c. 0
d. cannot be determined with out knowing the mass of the object
e. 6 mc038-4.jpg
Question 27
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A moving freight car runs into an identical car at rest on the track. The cars couple together. Compared to the velocity of the first car before the collision, the velocity of the combined cars after the collision is
Select one:
a. zero.
b. twice as large.
c. the same.
d. one half as large. Correct
Question 28
Correct
Mark 1.00 out of 1.00
Not flaggedFlag question
Question text
A ball of mass 0.4 kg is initially at rest on the ground.  It is kicked and leaves the kicker's foot with a speed of 5.0 m/s in a direction 60° above the horizontal.  The magnitude of the impulse imparted by the ball to the foot is most nearly
Select one:
a. mc030-1.jpg N s
b. 4 N s
c. 1 N s
d. mc030-2.jpg N s
e. 2 N s Correct
Question 29
Incorrect
Mark 0.00 out of 1.00
Not flaggedFlag question
Question text
mc052-1.jpg
A 2 kg ball collides with the floor at an angle q and rebounds at the same angle and speed as shown above.  Which of the following vectors represents the impulse exerted on the ball by the floor?
Select one:
a. mc052-3.jpg
b. mc052-4.jpg
c. mc052-2.jpg
d. mc052-6.jpg Incorrect
e. mc052-5.jpg