AP P1 MC TEST Answers

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?

0J

A student must analyze data collected from an experiment in which a block of mass 2M2M traveling with a speed v_0v0​ collides with a block of mass MM 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 2Mv_0=2Mv_f+Mv_f2Mv0​=2Mvf​+Mvf​ , because the blocks stick together after the collision

A block on a horizontal surface of negligible friction is placed in contact with an ideal spring, as shown above. The block is moved to the left so that the spring is compressed a distance xx from equilibrium and then released from rest. The block has kinetic energy K_1K1​ when it separates from the spring. When the spring is compressed a distance 2x2x and the block is released from rest, the kinetic energy of the block when it separates from the spring is

4K1

An automobile traveling on a straight, level road has an initial speed vv when the brakes are applied. In coming to rest with a constant acceleration, it travels a distance xx . How far would the automobile travel in coming to rest if it had the same acceleration but an initial speed 2v2v ?

4x

In which of the following situations is the kinetic energy of the object decreasing?

A baseball is heading upward after being thrown at an angle

An object is moving to the right with speed v_ivi​ when a force of magnitude FF is exerted on it. In which of the following situations is the object's direction of motion changing and kinetic energy decreasing a the instant shown?

Diagram 3

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.

Two particles collide and stick together. If no external forces act on the two particles, which of the following is correct for the change in total momentum \Delta pΔp and the change in total kinetic energy \Delta KΔK of the two particles?

Δp=0; ΔK<0

A block of mass 10 kg moves from position A to position B shown in the figure above. The speed of the block is 10 m/s at A and 4.0 m/s at B. The work done by friction on the block as it moves from A to B is most nearly

−220 J

A 50 kg athlete running at speed v grabs a light rope that hangs from a 10-meter-high platform and swings to a maximum of 1.8 m above the ground. Later, a 100 kg athlete, running at the same speed, grabs a similar rope hanging from a 5-meter-high platform. What is the maximum height to which the 100 kg athlete swings?

1.8m

A constant force of 900 N pushes a 100 kg mass up the inclined plane shown above at a uniform speed of 4 m/s. The power developed by the 900 N force is most nearly

3600W

A sled slides down a hill with friction between the sled and hill but negligible air resistance. Which of the following must be correct about the resulting change in energy of the sled-Earth system?

The sum of the kinetic energy and the gravitational potential energy changes by an amount equal to the energy dissipated by friction.

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?

+0.1m/s

A ball is dropped from rest and falls to the floor. The initial gravitational potential energy of the ball-Earth-floor system is 10 J. The ball then bounces back up to a height where the gravitational potential energy is 7 J. What was the mechanical energy of the ball-Earth-floor system the instant the ball left the floor?

7J

A cart is constrained to move along a straight line. A varying net force along the direction of motion is exerted on the cart. The cart's velocity vv as a function of time tt is shown in the graph above. The five labeled points divide the graph into four sections.For which segment does the cart move the greatest distance?

AB

A cart is moving on a level track in the positive xx-direction. A force acting parallel to the xx-axis is exerted on the cart. The graph above shows the net force exerted on the cart as a function of displacement. As the cart travels from x=0x=0 m to x=4x=4 m, what is the net change in the kinetic energy of the cart?

An increase in 10 J

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.

Which of the following is true of the conservation of momentum and kinetic energy?

Kinetic energy is conserved only in elastic collisions.

A crate is on a horizontal frictionless surface. A force of magnitude FF is exerted on the crate at an angle \thetaθ to the horizontal, as shown in the figure above, causing the crate to slide to the right. The surface exerts a normal force of magnitude F_NFN​ on the crate. As the crate slides a distance dd , it gains an amount of kinetic energy \Delta KΔK . While FF is kept constant, the angle \thetaθ is now doubled but is still less than 90\degree90° . Assume the crate remains in contact with the surface.As the crate slides a distance dd , how does the new gain in kinetic energy compare to \Delta KΔK ?

The new gain is less than \Delta KΔK

An empty sled of mass MM moves without friction across a frozen pond at speed v_0v0​ . Two objects are dropped vertically into the sled one at a time: first an object of mass mm and then an object of mass 2m2m . Afterward the sled moves with speed v_fvf​ . What would be the final speed of the sled if the objects were dropped into it in reverse order?

vF

A child slides from rest down slides A and B shown above. The slides are the same height, and the coefficient of friction between the slides and the child is the same. Which of the following compares the change in the kinetic energy of the child \Delta KΔK and the change in the potential energy of the child-Earth system \Delta UΔU for the two slides?

ΔKA​>ΔKB​ ; ΔUA​=ΔUB​

Two skaters are initially at rest next to each other on frictionless ice. Skater A pushes on skater B. If skater A has greater mass than skater B, which of the following correctly relates the magnitudes of their momenta pp and their kinetic energies KK after the push?

pA​=pB​; KA​<KB​

Three identical rocks are launched with identical speeds from the top of a platform of height h_0h0​ . The rocks are launched in the directions indicated above.Rock 1, of mass mm , reaches a maximum height h_{\max}hmax​ after being launched. During the time between the instant rock 1 is launched from height h_0h0​ and the instant it returns to height h_0h0​ , the work done on the rock by the gravitational force is

0

A rubber ball with mass 0.20 kg is dropped vertically from a height of 1.5 m above a floor. The ball bounces off of the floor, and during the bounce 0.60 J of energy is dissipated. What is the maximum height of the ball after the bounce?

1.2m

A forceFF is exerted on a 5 kg block to move it across a rough surface, as shown above. The magnitude of the force is initially 5 N, and the block moves at a constant velocity. While the block is moving, the force is instantaneously increased to 12 N. How much kinetic energy does the block now gain as it moves a distance of 2 m?

14j

A nonrotating spherical planet with no atmosphere has mass MM and radius RR . A projectile of mass mm is launched radially from the surface of the planet with initial speed v=\sqrt{\frac{GM}{2R}}v=2RGM​​ . The potential energy of the projectile-planet system, as a function of the projectile's distance rr from the center of the planet, is given by U=-G\frac{Mm}{r}U=−GrMm​ . The greatest distance from the center of the planet that the projectile reaches is

4/3 R

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 kg m/s

A block on a horizontal surface is placed in contact with a light spring with spring constantkk , as shown in figure 1. When the block is moved to the left so that the spring is compressed a distance dd from its equilibrium length, the potential energy stored in the spring-block system is E_mEm​ . When a second block of mass 2m2m is placed on the same surface and the spring is compressed a distance 2d2d , as shown in figure 2, how much potential energy is stored in the spring compared to the original potential energy E_mEm​ ? All frictional forces are considered to be negligible.

4em

An object initially at rest falls from a height HH until it reaches the ground. Two of the following energy bar charts represent the kinetic energy KK and gravitational potential energy U_gUg​ of the object-Earth system at two positions. The first position is when the object is initially released, and the second position is when the object is halfway between its release point and the ground. Which two charts could represent the mechanical energy of the object-Earth system? Select two answers.

Diagram 1

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 2 kg . Which of the following correctly describes the momentum \overrightarrow{p}p​ of the system and the kinetic energy KK of the system?

Only Momentum is Conserved

A cart of mass mm is moving with negligible friction along a track with known speed v_1v1​ to the right. It collides with and sticks to a cart of mass 4m4m moving with known speed v_2v2​ 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, because the momentum lost by one cart is gained by the other and there is only one unknown quantity.

Block 1 of mass m_1m1​ and block 2 of mass m_2m2​ are sliding along the same line on a horizontal frictionless surface when they collide at time t_CtC​ . The graph above shows the velocities of the blocks as a function of time. Which of the following is true of the motion of the center of mass of the two-block system during the time shown?

The center of mass moves at a constant velocity of +1.0+1.0 m/s because there is no friction acting on the system.

A cart is constrained to move along a straight line. A varying net force along the direction of motion is exerted on the cart. The cart's velocity vv as a function of time tt is shown in the graph above. The five labeled points divide the graph into four sections.During some part of the motion, the work done on the cart is negative. What feature of the motion indicates this?

The speed is decreasing

Block X slides along a horizontal surface with speed v_xvx​ toward block Y that is initially at rest, as shown in Figure 1. After block X collides with block Y, the two blocks remain stuck together and travel at a velocity v_{xy}vxy​ , as shown in Figure 2. Frictional forces are considered to be negligible. Which of the following claims is correct regarding the momentum of the system containing only block X and the system that contains block X and block Y?

The system containing block X is an open system, and the system of both blocks is a closed system.

A block of mass MM is sliding with an initial speed v_ivi​ along a horizontal surface with negligible friction. A constant force of magnitude F_AFA​ is exerted on the object at an upward angle of 60\degree60° from the horizontal, causing the object to speed up. If the block remains in contact with the floor, what is the change in the block's kinetic energy as it moves a horizontal distance \Delta xΔx ?

1/2Fa Delta A

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 relative to the ground. Which of the following is the best estimate of the velocity of the skateboard immediately after the dog has jumped?

17 m/s south

A rock of mass mm is thrown horizontally off a building from a height hh , as shown above. The speed of the rock as it leaves the thrower's hand at the edge of the building is v_0v0​ . What is the kinetic energy of the rock just before it hits the ground?

1\2mv^2 + mgh

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 Ns

A 2 kg object is released from rest near and above Earth's surface such that the object-Earth system's gravitational potential energy as a function of time is shown in the graph. Which of the following graphs represents the kinetic energy of the object as a function of time? Assume all frictional forces are considered to be negligible.

Diagram 2 THe graph that is parabolic going upwards as time increases o -> 10000 Postive

A student stands at one end of a raft floating in a pool with equally spaced marks along the bottom, as shown above. The student and the raft have the same mass. The student walks to the opposite end of the raft. Which of the following best shows the final locations of the raft and student relative to the marks at the bottom of the pool? Assume that there is no drag force between the raft and the water.

Diagram 4 Answer: The guy standing on the boat if looking right to left the guy is on the 3rd tick mark. DO NOT count the edge that looks like an L as 1.

Just want to let yall know that one of the questions it says there is 2 results but its the same its like 1/2mv something

Ill try and explain the diagrams.

A person holds a book at rest a few feet above a table. The person then lowers the book at a slow constant speed and places it on the table. Which of the following accurately describes the change in the total mechanical energy of the Earth-book system?

The total mechanical energy decreases, because the person does negative work on the book by exerting a force on the book in the direction opposite to its displacement.

An inclined track is secured to a table. The height of the highest point of the track above the tabletop is h_1h1​ . The height from the tabletop to the floor is h_2h2​ . A block of mass MM is released from rest and slides down the track such that all frictional forces are considered to be negligible. The block leaves the track horizontally and strikes the ground at a distance DD from the edge of the track as shown. Which of the following statements are correct about the scenario? Select two answers

The total mechanical energy of the system containing only the block increases from the moment of release to the moment it strikes the ground. The total mechanical energy of the block-Earth system remains constant.

A block of mass 0.10 kg is attached and secured to one end of a spring with spring constant 50 N/m. The other end of the spring is secured to a wall. The block is pushed against the spring, which compresses the spring to a position of x=-0.04x=−0.04 m. When uncompressed, the end of the spring that is attached to the block is at a position of x=0.00x=0.00 m. The block-spring system is then released from rest, and the block travels along a horizontal, rough track. A motion sensor is placed so that it measures the velocity of the object as it slides along the track. A graph of total mechanical energy of the block-spring system as a function of position is shown. Which of the following statements about the block-spring system are true? Select two answers

The work done by friction as the block travels from x=-0.04x=−0.04 m to x=-0.02x=−0.02 m is 0.01 J The force exerted on the block by the spring at x=-0.02x=−0.02 m is 1 N.

A spaceship and its shuttle pod are traveling to the right in a straight line with speed vv , as shown in the top figure above. The mass of the pod is mm , and the mass of the spaceship is 6m6m . The pod is launched, and afterward the pod is moving to the right with speed v_pvp​ and the spaceship is moving to the right with speed where v_f>vvf​>v , as shown in the bottom figure. Which of the following is true of the speed v_cvc​ of the center of mass of the system after the pod is launched?

Vc = V