physics MCQ key
Which quantity should the student measure, if any, to determine whether the conservation of momentum applies to the two-block system from immediately before the collision to immediately after the blocks have reached the top of the ramp while stuck together? Justify your selection.
The velocity vR of the two-block system at the top of the ramp, because this can be used to determine the final momentum of the system.
Ball X of mass 1.0 kg and ball Y of mass .5 kg travel toward each other on a horizontal surface...
ball Y will travel at a speed greater
The graph above shows the position x as a function of time for the center of mass of a system of particles of total mass of 6.0 kg. For a very short time interval around 2.0 s, an external force is exerted on an object in the system. What is the resulting change in the momentum of the system?
-18
A ball of mass M and speed v collides head-on with a ball of mass 2M and speed v/2 , as shown above. If the two balls stick together, their speed after the collision is
0
A dog of mass 10 kg sits on a skateboard of mass 2 kg that is initially traveling south at 2 m/s. The dog jumps off with a velocity of 1 m/s north rela-tive to the ground. Which of the following is the best estimate of the velocity of the skateboard immediately after the dog has jumped?
17
A 2 kg object traveling at 5 m/s on a frictionless horizontal surface collides head-on with and sticks to a 3 kg object initially at rest. Which of the following correctly identifies the change in total kinetic energy and the resulting speed of the objects after the collision?
Decreases, 2 m/s
A ball is dropped and bounces off the floor. Its speed is the same immediately before and immediately after the collision.
The ball's momentum changes direction but not magnitude
A student performs an experiment in which two blocks, block X of mass 2kg and block Y of mass 3kg, are tied together by a rope. The system containing Block X and Block Y is dropped above Earth's surface in the orientation shown in Figure 1. A motion detector below each block collected data that were graphed to show the velocity as a function of time for Blocks X and Y as they fell toward the ground. The graphs are shown in Figure 2 and Figure 3, respectively. The positive direction is considered to be down. The change in momentum for the system containing block X and block Y is most nearly
250
A person of mass 60 kg sliding along level ice at a speed of 3.0 m/s collides with a second person who is initially at rest. Assume that friction is negli-gible. If the two people hold onto each other and their common final speed after colliding is 2.0 m/s, the mass of the second person is
30
A force probe is used to push a box across a smooth surface, as shown in the figure. Frictional forces are considered to be negligible. The force probe collects data about the force exerted on the box as a function of time. The data are used to create the graph that is shown. During which time interval does the box experience the greatest change in its momentum?
4-6s
The graph above shows the rate of change of linear momentum of the sphere of mass m as a function of time. What is the linear momentum of the two-sphere system at time t = 3.0 s?
45
A student obtains data on the magnitude of force applied to an object as a function of time and displays the data on the graph above. Answer the following question for the information and diagram above. The increase in the momentum of the object between t = 0 s and t = 4 s is most nearly
60 N*s
A 2kg object travels in the positive direction across a horizontal surface with a constant speed of 10 m/s . A force is exerted on the object for 4s, and the force increases linearly with respect to time. The table shows data about the magnitude of the applied force exerted on the object at different times. The force is exerted on the object in the opposite direction of the object's displacement. What is the change in momentum of the object?
8 negative
A student conducts three experiments in which a cart of mass M is pushed along a horizontal surface of negligible friction for 20s by an applied force. The graph shows the force as a function of time for each experiment. Which of the following correctly ranks the greatest change in the cart's momentum from 0s to 20s?
=,=
A cart of mass 1kg travels along a horizontal, frictionless surface. A net force is applied to the cart. A graph of the net force applied to the cart as a function of time is shown. The initial and final direction of the cart and the direction of the net force exerted on the cart are unknown. The distance of one grid unit represents a change in velocity of 1 m/s. Which of the following diagrams could represent the direction and relative magnitude of the velocity of the cart before the force is applied and after the force is applied? Select two answers.
AD
An experiment is performed in which a collision occurs between cart X and cart Y . Data are collected about each cart before and after a collision takes place. Which data from the table should the student use to verify the conservation of momentum for each trial, and what is a justification for using those data?
All data are necessary to verify the conservation of momentum, because all information for each cart should be known.
Claim 1: Change in linear momentum of the center of mass of the system from 0.0s to 0.5s can be determined. Claim 2: The average applied force exerted on the center of mass of the system from 0.0s to 0.5s can be determined. Claim 3: The change in the kinetic energy of the system from 0.0s to 0.5s can be determined. Which of the student's claims are correct?
1,2,3
A 0.050 kg tennis ball is moving to the left at 10 m/s when it is hit by a tennis racket that is moving to the right. The magnitude of the force exerted on the ball by the racket as a function of time is shown in the figure above. What is the speed of the ball after the collision with the racket?
30
A student conducts an experiment to verify that a collision is elastic. The two objects, object X and object Y , travel toward each other, as shown in the figure. The mass and the initial speed of both objects are known. Which of the following equations should the student consider using to verify that the collision is elastic, and why?
Equation II and equation III, because the conservation of momentum must be verified for the system of object X and object Y, and the difference in the kinetic energy of the system before and after the collision should be determined.
How does an air mattress protect a stunt person landing on the ground after a stunt?
It lengthens the stopping time of the stunt person and reduces the force applied during the landing.
Cart A with a mass of 2.0 kg travels at a constant speed of 3.0 m/s to the right on a horizontal surface, as shown in the figure. Cart A then collides with cart B with a mass of 1.5 kg that is initially at rest...
Equation 1 and Equation 2
A student must determine a nonzero change in momentum of an object for a specific interval of time. Which of the following experiments could the student conduct? Select two answers.
drop a ball and give a block
A cart of mass m is moving with negligible friction along a track with known speed v1 to the right. It collides with and sticks to a cart of mass 4m moving with known speed v2 to the right. Which of the two principles, conservation of momentum and conservation of mechanical energy, must be applied to determine the final speed of the carts, and why?
only conservation of momentum
Assume that the collision in each scenario is elastic. A graph of the magnitude of the force exerted on Cart Y as a function of time for scenario 1 is shown. During which interval of time does the magnitude of the momentum of Cart Y change the most?
.004s to .006s
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
2 N*s
During an experiment, a student records the net horizontal force exerted on an object moving in a straight line along a horizontal frictionless track. The graph above shows the force as a function of time. Of the following, which is the best approximation of the magnitude of the change in momentum of the object between 0 s and 4 s?
30
In an experiment, two objects, object X and object Y, travel toward each other and collide. Data are collected about each object before, during, and after the collision, as shown in the table. Which of the following pairs of data, when used together to create two graphs, could verify the conservation of momentum? Select two answers.
average force, average force
A railroad car of mass m is moving with speed v when it collides with and connects to a second railroad car of mass 3m, initially at rest, as shown above. How do the speed and kinetic energy of the connected cars compare to those of the single car of mass m before the collision?
less less
Block 1 of mass m1 and block 2 of mass m2 are sliding along the same line on a horizontal frictionless surface when they collide at time tc. The graph above shows the velocities of the blocks as a function of time. How does the kinetic energy of the two-block system after the collision compare with its kinetic energy before the collision, and why?
It is less, because the blocks have the same velocity after the collision, so some of their kinetic energy was transformed into internal energy.
A kitten sits in a lightweight basket near the edge of a table. A person accidentally knocks the basket off the table. As the kitten and basket fall, the kitten rolls, turns, kicks, and catches the basket in its claws. The basket lands on the floor with the kitten safely inside. If air resistance is negligible, what is the acceleration of the kitten-basket system while the kitten and basket are in midair?
The acceleration is directed downward with magnitude equal to g because the system is a projectile.
Object X of mass m0 travels to the right with a velocity v0. Object Y of mass 2m0 moves to the left at 2v0, as shown in the figure. The objects collide and then stick together. What is the change in kinetic energy of the two-object system from immediately before the collision to immediately after the collision?
The kinetic energy decreases by 3m0v20 .
Consider the situation in which the objects collide but do not stick together. Which of the following predictions is true about the center of mass of the two-object system immediately after the collision?
does not change
Consider the situation in which object X has a speed of 2m/s and object Y has a speed of 5m/s after the collision takes place. After the collision, both objects travel in the same direction. Which of the following predictions must be true about how the momentum p of the two-object system and the kinetic energy K of the two-object system change from before the collision to after the collision?
remains remains
A spaceship and its shuttle pod are traveling to the right in a straight line with speed v, as shown in the top figure above. The mass of the pod is m, and the mass of the spaceship is 6m. The pod is launched, and afterward the pod is moving to the right with speed vp and the spaceship is moving to the right with speed where vf > v, as shown in the bottom figure. Which of the following is true of the speed vc of the center of mass of the system after the pod is launched?
vc = v
An empty sled of mass M moves without friction across a frozen pond at speed v0. Two objects are dropped vertically into the sled one at a time: first an object of mass m and then an object of mass 2m. Afterward the sled moves with speed vf. What would be the final speed of the sled if the objects were dropped into it in reverse order?
vf
Consider the situation in which the objects collide and stick together. Which of the following predictions is true about the center of mass of the two-object system immediately after the collision?
does not change
An object of mass 2 kg collides with an object of mass 1 kg that is at rest, as shown in the figure. A graph of the force as a function of time that the 1 kg object exerts on the 2 kg object is shown.
(2 kg) (2m/s-v0)=1/2(8000 N)(0.00125 s)
In an experiment, a variable net force is applied to an object. A graph of the net force exerted on the object as a function of time is shown. Which of the following experiments could have been conducted to represent the variable net force shown in the graph?
3kg
Object X of mass 4 kg travels with a speed of 3 m/s toward object Y of mass 2 kg that is initially at rest. Object X then collides with and sticks to object Y. After the collision, object X and object Y remain stuck together. How much mechanical energy is converted into nonmechanical energy during the collision?
6 J
A ball is released from rest above a horizontal surface. The ball falls downward and collides with the surface with a speed of 2.0m/s. The average force exerted during the collision is 20N over a time interval of 0.1s. Which of the following best predicts what will happen to the ball immediately after the collision?
The ball will come to rest on the surface
Two identical carts are free to move along a straight frictionless track. At time t1, cart X is moving at 2.0 m/s when it collides with and sticks to cart Y, which is initially at rest. Which of the following graphs best shows the velocity of cart X before and after the collision?
2 -> 1
A student plans to conduct an experiment in which the momentum of a two-object system can be determined immediately before and after a collision takes place. The student slides block X at an unknown constant speed toward an identical block, block Y , that is initially at rest, as shown in the figure. There is negligible friction between the blocks and the surface.
Mass balance, meterstick, and stopwatch
Consider the scenario in which block X is released from rest at a height H2, which is lower than H1 but higher than h. Which of the following statements is true about the horizontal distance traveled by block Y as a projectile in the two scenarios? Assume the collision in both scenarios is elastic.
The horizontal distance will be greater for block Y when block X is released from height H1.
Two identical spaceships are traveling in deep space, far from any planets or stars. The ships travel in the same direction, with the slower one directly behind the faster one. The ships are connected by a cable attached to a spool, so that the part of the cable outside the ships can be made longer or shorter as needed. The cable is used to bring the ships to the same speed for a transfer of cargo. The graph above shows the speed of the two ships during a 10 s interval. Does at least one of the ships have its engine turned on during the time interval shown, and what evidence indicates so?
Yes, because the momentum of the two-rocket system increases
A 1.0 kg lump of clay is sliding to the right on a frictionless surface with speed 2 m/s . It collides head-on and sticks to a 0.5 kg metal sphere that is sliding to the left with speed 4 m/s . What is the kinetic energy of the combined objects after the collision?
0 J
Two identical blocks with mass 5.0 kg each are connected to the opposite ends of a compressed spring. The blocks initially slide together on a frictionless surface with velocity 2 m/s to the right. The spring is then released by remote control. At some later instant, the left block is moving at 1 m/s to the left, and the other block is moving to the right. What is the speed of the center of mass of the system at that instant?
2 m/s
Block A of mass 2.0 kg is released from rest at the top of a 3.6 m long plane inclined at an angle of 30º, as shown in the figure above. After sliding on the horizontal surface, block A hits and sticks to block B, which is at rest and has mass 3.0 kg. Assume friction is negligible. The speed of the blocks after the collision is most nearly
2.4 m/s
A person applies an impulse of 5.0 kg∙m/s to a box in order to set it in motion. If the person is in contact with the box for 0.25 s, what is the average force exerted by the person on the box?
20.0N
A 12 kg box sliding on a horizontal floor has an initial speed of 4.0 m/s. The coefficient of friction between the box and the floor is 0.20. The box moves a distance of 4.0 m in 2.0 s. The magnitude of the change in momentum of the box during this time is most nearly
48
Assume that the collision in each scenario is elastic. How does the magnitude of the change in the momentum Δp of Object Y compare for each scenario?
Δp3>Δp1>Δp2
A spacecraft of mass 4000 kg is traveling in a straight line in the positive direction. Engines can be fired so that the force exerted on the spacecraft is in the positive or negative direction. The graph above shows data for the force during one interval. Which of the following is the best estimate of the net change in the speed of the spacecraft from time t = 0 to time t = 4 s?
+.1m/s
Block X of mass 2kg and block Y of unknown mass travel toward each other. An elastic collision occurs in which momentum is conserved. The graph shows the velocity of block X and of velocity of block Y as a function of time before, during, and after the collision. What is the mass of block Y ?
6 kg
Block X of mass 4M travels at a speed 5v0 toward block Y of mass M , which is initially at rest. After block X elastically collides with block Y , block X has a speed of 3v0 in the same direction as before the collision. What is the speed of block Y immediately after the collision?
8v0
Object X of mass M travels toward object Y of mass 2M in such a way that they collide. The table contains data about the velocities of object X and object Y immediately before the collision and immediately after the collision. What are the change in momentum of the two-object system and the change in momentum of each object from immediately before the collision to immediately after the collision?
A
Two identical spaceships are traveling in deep space, far from any planets or stars. The ships travel in the same direction, with the slower one directly behind the faster one. The ships are connected by a cable attached to a spool, so that the part of the cable outside the ships can be made longer or shorter as needed. The cable is used to bring the ships to the same speed for a transfer of cargo. The graph above shows the speed of the two ships during a 10 s interval. Which of the following graphs best represents the net force Fnet exerted on the two-ship system?
C (straight Line at y=3)
A force of constant magnitude F and fixed direction acts on an object of mass m that is initially at rest. If the force acts for a time interval ∆t over a displacement ∆x , what is the magnitude of the resultant change in the linear momentum of the object?
FΔt
Three objects can only move along a straight, level path. The graphs below show the position d of each of the objects plotted as a function of time t.
III Only
Block X of mass M travels in the positive direction with a speed vX toward block Y of mass M that is at rest, as shown in Figure 1. After the collision, block Y travels with a speed of vY in the positive direction while block X remains at rest. The horizontal surface that the blocks slide across is considered to be smooth. How can a student determine whether the collision is elastic or inelastic?
The masses of both blocks are known, and the initial and final velocities are both blocks are known. Therefore, the student must compare the initial kinetic energy of the two-block system before the collision and after the collision using \Delta K=\frac{1}{2}m\Delta v^2ΔK=21mΔv2
A group of students conducts an experiment in which two carts collide with each other as they travel across a horizontal surface with negligible friction. Using motion detectors and a mass balance, the students collect data about the carts immediately before and immediately after the collision, as shown in the table. Which of the following claims is true regarding the momentum and the kinetic energy of the two-cart system for the experiment? Does the data indicate that a net external force acts on the system?
The momentum is different and the total kinetic energy of the system is different immediately before the collision and immediately after the collision. This indicates that a net external force is exerted on the system.
The student conducts a second experiment in which the magnitude of the force exerted on block X from block Y is measured over the time in which the collision takes place. A graph of the force as a function of time is shown. In a third experiment, the student creates a collision such that the force exerted on block X from block Y is constant for 0.020 s. Which of the following constant forces, if exerted on block X from block Y, would produce the same change in momentum as is shown by the graph?
200N
Block 1 of mass m1 and block 2 of mass m2 are sliding along the same line on a horizontal frictionless surface when they collide at time tc. The graph above shows the velocities of the blocks as a function of time.
Block 2, because the final velocity is closer to the initial velocity of block 2 than it is to the initial velocity of block 1
A student must conduct an experiment to verify the conservation of momentum for a closed two-cart system. Cart X and cart Y travel toward each other and eventually collide, as shown in the figure. The student has determined the following procedure.
Conduct the experiment on a smooth, level surface.
Which of the following is a true statement about the conservation of linear momentum?
It is conserved only when no net external force acts on the system under consideration.
An object of known mass M with speed vo travels toward a wall. The object collides with it and bounces away from the wall in the opposite direction in which the object was initially traveling. The wall exerts an average force Fo on the object during the collision. A student must use the equation \Delta p=F\Delta tΔp=FΔt to determine the change in momentum of the object from immediately before the collision to immediately after the collision. Which side of the equation could the student use to determine the change of the object's momentum?
Neither side of the equation may be used because there are too many unknown quantities before, during, and after the collision.
Two model cars, A and B, have the same mass but different bumpers. The acceleration of each car during its collision with a wall is measured, and the data are shown in the graphs above. Which of the following statements about the collisions are correct? Select two answers.
The cars, the change
In an experiment, an object is released from rest near and above Earth's surface. A student must determine the relationship between the direction of the gravitational force exerted on the object and the change in momentum caused by that force. What data could the student collect to determine the magnitude and direction of the gravitational force and the change in momentum of the object? Justify your choices. Select two answers.
The mass of the object, because it is required to determine the force due to gravity exerted on the object, and the velocity of the object the instant before it reaches Earth's surface, because it is required to determine the change in velocity of the object. The mass of the object, because it is required to determine the force due to gravity exerted on the object, and the distance fallen by the object, because the force is exerted during the entire falling distance.
A soft foam block of mass m slides without friction in the positive x-direction with speed v. At time t = 0, a student briefly pushes the block with a force probe in the positive x-direction. The graph above shows the force probe's measurements as a function of time during the push. Which of the following statements is true about the block's momentum between t = 0 and t = t1?
The momentum of the block has increased by approximately 1/2 F0t1
The student uses the data collected from the experiment to create the data table. Which of the following statements is true regarding the data?
The momentum of the two-block system is not conserved because the initial momentum of the system is not equal to the final momentum of the system
A student drops an object from rest above a force plate that records information about the force exerted on the object as a function of time during the time interval in which the object is in contact with the force plate. Which of the following measurements should the student take, in addition to the measurements from the force plate, to determine the change in momentum of the object from immediately before the collision to immediately after the collision?
The student has enough information to make the determination.
Two blocks are on a horizontal, frictionless surface. Block A is moving with an initial velocity of v0 toward block B, which is stationary, as shown above. The two blocks collide, stick together, and move off with a velocity of v0/3 . Which block, if either, has the greater mass?
block B
Graphs I , II , and III that are shown represent momentum versus time graphs for three possible cases in which a collision could occur between two carts. Which of the momentum versus time graphs are possible representations of one of the three scenarios if the system is closed?
graphs I and III only
An object of mass 5kg travels in the positive direction with a speed of 1m/s. The object collides with a second object that exerts an average net force over an interval of time such that the 5kg object comes to rest. Which of the following best predicts the change in momentum for the 5kg object?
in the negative direction
In a one-dimensional perfectly elastic collision, an object of mass m is traveling with speed v0 in the +x-direction when it strikes an object with mass 3m that is at rest. What are the objects' velocities following the collision?
vo/2, -x-direction vo/2, +x-direction
A cart of known mass moves with known speed along a level, frictionless track, as shown in the figure above. The cart hits a force sensor and rebounds. The force sensor measures the force exerted on the cart as a function of time and as a function of the position of the cart. The results will be graphed on the axes shown. Which of the two graphs can be used to determine the cart's speed after it rebounds?
Either
A dart of mass md is launched straight upward toward a block of mass mb that hangs at rest from a string, as shown in Figure 1. Immediately before the dart collides with the block, the dart has a speed v0. The dart then collides with and sticks to the block, and the dart-block system travels upward to a height H before the system comes to rest, as shown in Figure 2. What is the change in momentum of the dart-block system immediately before the collision to the instant when the system comes to rest?
-mdvo
A toy cannon of mass 1.0 kg is initially at rest on a horizontal surface when it launches a 0.05 kg projectile with a velocity of 10 m/s at an angle of 60° above the horizontal. What is the speed of the 1.0 kg cannon immediately after the projectile is released, assuming that friction is negligible?
.25
A 2kg object travels across a horizontal surface with a constant speed of 6 m/s. An applied force that increases with time is then exerted on the object. A graph of the force exerted on the object as a function of time is shown. The applied force is in the direction of the object's displacement. All frictional forces are considered to be negligible. What is the object's speed after the force has been applied for 4s?
22
A student must analyze data collected from an experiment in which a block of mass 2M traveling with a speed v0 collides with a block of mass M that is initially at rest. After the collision, the two blocks stick together. Which of the following applications of the equation for the conservation of momentum represent the initial and final momentum of the system for a completely inelastic collision between the blocks? Justify your selection. Select two answers.
2Mv0=3Mvf , because the blocks stick together after the collision. 2Mv0=2Mvf+Mvf , because the blocks stick together after the collision.
A student must conduct an experiment in which a block is pulled across a horizontal surface by a spring scale so that a nonzero change in momentum of the block can be determined for a specific time interval. The student also has access to measuring tools that are found in a typical physics laboratory. Which of the following experiments could the student conduct to determine the change in momentum of the cart? Select two answers.
Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Record the force that the spring scale exerts on the block. Use a stopwatch to determine the time that the block is in motion. Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Use the motion detector to record the speed of the block at the beginning of the time interval and at the end of the time interval. Use a mass balance to measure the mass of the block.
A student conducts an experiment in which an object travels across a horizontal surface while for 2s a net force is applied to a 2 kg object that initially travels with a speed of 0.5 m/s. Data collected from the experiment are used to create the graph of the magnitude of the applied force exerted on the object as a function of time is shown. All frictional forces are considered to be negligible. Can the student use the graph and the known data to determine the momentum of the object after the force has been applied?
No, because the student needs to know the direction that the force is applied to the object because the applied force will be in the same direction as the change in momentum of the object.
In an experiment, a spring is placed between object X and object Y . Object X has twice the mass of object Y , which has mass M . The two objects are pushed together until the spring is at its maximum compression, as shown in the figure. The objects are released from rest, and data are collected for the speed of each object immediately after the spring is no longer compressed. However, the graph does not indicate which object corresponds to a given velocity, and the positive direction is not indicated. Which of the following correctly describes the velocities of object X and object Y after the collision?
Object X travels at −2 m/s and object Y travels at 4 m/s after the spring is no longer compressed
An object is used in three different experiments so that a student can analyze the motion of the object when a net force is exerted on it. The data obtained from the three experiments are shown in the table. How can the student use the data to determine the relationship between the object's change in momentum and the direction of the net force exerted on the object?
The student...
A projectile fired into the air explodes and splits into two halves of equal mass that hit the ground at the same time. If the projectile had not exploded, it would have landed at point X, which is a distance R to the right of the launch point. After the explosion, one of the halves lands at point Y, which is a distance 2R to the right of the launch point. If air resistance is negligible, where did the other half land?
at
A student must conduct an experiment to verify the conservation of momentum for a closed two-cart system. Cart X and cart Y travel toward each other and eventually collide, as shown in the figure. Data collected from the experiment are shown in the table. What additional measuring tool should the student have used in order to verify the conservation of momentum?
balance
Object X travels across a horizontal surface and collides with object Y. The velocity as a function of time for object X and object Y before, during, and after the collision is shown in the graph. Both objects have a mass of 2kg. Which of the following correctly describes the momentum p⃗ of the system and the kinetic energy K of the system?
conserved, not conserved
An ice-skater is moving at a constant velocity across an icy pond. The skater throws a snowball directly ahead. Which of the following correctly describes the velocity of the center of mass of the skater-snowball system immediately after the snowball is thrown? Assume friction and air resistance are negligible.
it is equal to the original velocity of the skater
A student performs an experiment in which a 4kg object travels across a horizontal surface with an initial speed velocity of 6m/s and a 2kg object travels across a horizontal surface with an initial speed velocity of −3m/s. The objects travel toward each other and collide. Data collected from the experiment were used to create the velocity versus time graph shown that contains information about both objects before and after the collision. The positive direction is considered to be to the right. Which of the following statements are true regarding the data from the experiment?
the velocity
Two carts, of mass 2m and m, approach each other head-on with the same speed v, as shown in the figure above. When the carts collide, they hook together. Assuming positive momentum is to the right, which of the following best represents the momentum of the cart of mass m as a function of time before and after the collision?
y=-3->y=1
