Physics 1 Second Test (Conceptual & PreLecture)

A 4.0-kg object is moving with speed 2.0 m/s. A 1.0-kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping?

Both travel the same distance

For an elastic collision, which of the following statements are true? Kinetic energy is lost. Momentum is lost. Momentum is gained. Kinetic energy is conserved. Kinetic energy is gained. Momentum is conserved.

Kinetic energy is conserved. Momentum is conserved.

For an INELASTIC collision, which of the following statements are true?

Kinetic energy is lost., Momentum is conserved.

A stock person at the local grocery store has a job consisting of the following five segments:(1) picking up boxes of tomatoes from the stockroom floor(2) accelerating to a comfortable speed(3) carrying the boxes to the tomato display at constant speed(4) decelerating to a stop(5) lowering the boxes slowly to the floor.During which of the five segments of the job does the stock person do positive work on the boxes?

1 and 2

Suppose we repeat the experiment from the video, but this time we use a rocket three times as massive as the one in the video, and in place of water we use a fluid that is twice as massive (dense) as water. If the new fluid leaves the rocket at the same speed as the water in the video, what will be the ratio of the horizontal speed of our rocket to the horizontal speed of the rocket in the video after all the fluid has left the rocket? (Ignore air resistance.)

2/3 (The rocket's speed is proportional to the ratio of the fluid's mass to the rocket's mass.)

Which of the following statements is/are true?

A conservative force permits a two-way conversion between kinetic and potential energies. The work done by a nonconservative force depends on the path taken .A potential energy function can be specified for a conservative force.

Two stones, one of mass mm and the other of mass 2mm, are thrown directly upward with the same velocity at the same time from ground level and feel no air resistance. Which statement about these stones is true?

At its highest point, the heavier stone will have twice as much gravitational potential energy as the lighter one because it is twice as heavy.

Two identical balls are thrown directly upward, ball A at speed vv and ball B at speed 2vv, and they feel no air resistance. Which statement about these balls is correct?

Ball BB will go four times as high as ball AA because it had four times the initial kinetic energy.

Immediately after being launched horizontally to the right, in what direction does the acceleration vector point?

Downward

Imagine that you replace the block in the video with a happy or sad ball identical to the one used as a pendulum, so that the sad ball strikes a sad ball and the happy ball strikes a happy ball. The target balls are free to move, and all the balls have the same mass. In the collision between the sad balls, how much of the balls' kinetic energy is dissipated?

Half of it

For an elastic collision, which of the following statements are true?

Momentum is conserved, Kinetic energy is conserved.

Now, consider the collision between two happy balls described in Part A. How much of the balls' kinetic energy is dissipated?

None of it

Person B does twice the work of person A, and in one-half of the time . How does the power output of person B compare to person A?

Person B has four times the power output of person A.

The video shows an animated billiards experiment in which a cue ball strikes a glued-in-place eight-ball. Which of the following explains why the momentum of the eight-ball is conserved? The "glue force" cancels the collision force. The eight-ball is an isolated system. The collision is elastic. The cue ball rebounds with the same speed it had coming in.

The "glue force" cancels the collision force.

Which of the following statements is/are true? - The SI unit of power is the watt. - A person is limited in the total work he or she can do by their power output. - Power is the rate at which work is done. - The SI unit of power is the horsepower. - Power is the rate at which energy is transformed.

The SI unit of power is the watt., Power is the rate at which work is done, Power is the rate at which energy is transformed.

Two identical balls are thrown vertically upward. The second ball is thrown with an initial speed that is twice that of the first ball. How does the maximum height of the two balls compare?

The maximum height of the second ball is four times that of the first ball.

A lump of putty and a rubber ball have equal mass. Both are thrown with equal speed against a wall. The putty sticks to the wall. The ball bounces back at nearly the same speed with which it hit the wall. Which object experiences the greater momentum change?

The ball experiences the greater momentum change.

Jacques and George meet in the middle of a lake while paddling in their canoes. They come to a complete stop and talk for a while. When they are ready to leave, Jacques pushes George's canoe with a force F⃗ F→ to separate the two canoes. What is correct to say about the final momentum and kinetic energy of the system if we can neglect any resistance due to the water?

The final momentum is zero but the final kinetic energy is positive.

A potential energy function for system 1 is given by U1(x) = Cx2 + Bx3. The potential energy function for system 2 is given by U2(x) = A + Cx2 + Bx3, where A is a positive quantity. How does the force on system 1 relate to the force on system 2 at a given position?

The force is identical on the two systems.

Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greatest impact force?

The force would be the same in both cases.

What represents the impulse of the force in a graph of force versus time?

The impulse is equal to the area under the curve.

In a lab environment, you are investigating the impulse of a force exerted on a brick when the brick's speed is reduced from 2.5 m/s to a complete stop. First, you allow the brick to slam into a secured piece of wood, bringing the brick to a sudden stop. Second, you allow the brick to plow into a large slab of gelatin so that the brick comes to a gradual halt. In which situation is there a greater impulse of the force on the brick?

The impulse is the same in both situations.

Which statement must be true for the momentum of a system to be conserved? The net external force on the system is zero. There are no external forces acting on the system. The internal forces sum to zero. The net external force on the system is non-zero.

The net external force on the system is zero.

A person applies a 50 N force on a crate, causing it to move horizontally at a constant speed through a distance of 10 m. What is the net work done on the crate?

The net work done on the crate is zero joules.

If the net work done on an object is positive, what can you conclude about the object's motion?

The object is speeding up.

If the net work done on an object is zero, what can you determine about the object's kinetic energy?

The object's kinetic energy remains the same.

While goofing off at the ice skating rink, a student takes off her shoes and places each of them on the ice. Her friend, a hockey player, then shoots a hockey puck at each shoe. The first puck immediately comes to rest after it collides with the left shoe. The second puck rebounds after it collides with the right shoe. If each hockey puck has the same incoming speed, which shoe has greater speed after the collision?

The right shoe

A small car has a head-on collision with a large truck. Which of the following statements concerning the magnitude of the average force due to the collision is correct?

The small car and the truck experience the same average force.

A freight car moves along a frictionless level railroad track at constant speed. The freight car is open on the top. A large load of sand is suddenly dumped into the freight car. What happens to the speed of the freight car?

The speed of the freight car decreases.

A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case, and air resistance is negligible.Case A: Thrown straight up.Case B: Thrown straight down.Case C: Thrown out at an angle of 45° above horizontal.Case D: Thrown straight out horizontally.In which case will the speed of the stone be greatest when it hits the water below?

The speed will be the same in all cases

Which of the following statements is/are true? The total mechanical energy of a system, at any one instant, is either all kinetic or all potential energy. The total mechanical energy of a system is constant only if conservative forces do work. The total mechanical energy of a system is constant only if nonconservative forces do work. Mechanical energy can be dissipated to nonmechanical forms of energy. The total mechanical energy of a system is equally divided between kinetic and potential energy.

The total mechanical energy of a system is constant only if conservative forces do work. Mechanical energy can be dissipated to nonmechanical forms of energy.

When a person steps forward out of a small boat onto a dock, the boat recoils backward in the water. Why does this occur?

The total momentum of the system is conserved.

Which of the following statements are true? Select all correct responses.

The vector sum of forces acting on a particle equals the rate of change of momentum of the particle with respect to time. The total momentum of any number of particles is equal to the vector sum of the momenta of the individual particles. The total momentum of an isolated system is constant.

A red ball with a velocity of +3.0 m/s collides head-on with a yellow ball of equal mass moving with a velocity of −2.0 m/s. What is the velocity of the two balls after the elastic collision?

The velocity of the red ball is −2.0 m/s; the velocity of the yellow ball is +3.0 m/s.

Which of the following statements is/are true? A potential energy function can be specified for a nonconservative force. A nonconservative force permits a two-way conversion between kinetic and potential energies. The work done by a nonconservative force depends on the path taken. A potential energy function can be specified for a conservative force. A conservative force permits a two-way conversion between kinetic and potential energies. The work done by a conservative force depends on the path taken.

The work done by a nonconservative force depends on the path taken. A potential energy function can be specified for a conservative force. A conservative force permits a two-way conversion between kinetic and potential energies.

A graph depicts force versus position. What represents the work done by the force over the given displacement?

The work done is equal to the area under the curve.

An object weighing 20 N moves horizontally toward the right a distance of 5.0 m. What is the work done on the object by the force of gravity?

The work done on the object by the force of gravity is zero joules.

Three cars (car FF, car GG, and car HH) are moving with the same velocity when the driver suddenly slams on the brakes, locking the wheels. The most massive car is car FF, the least massive is car HH, and all three cars have identical tires.(a) Which car travels the longest distance to skid to a stop? b) For which car does friction do the largest amount of work in stopping the car?

They all travel the same distance in stopping. Car F

When an object is solely under the influence of conservative forces, the sum of its kinetic and potential energies does not change.

True

The planet Earth travels in a circular orbit at constant speed around the Sun. What is the net work done on the Earth by the gravitational attraction between it and the Sun in one complete orbit? Assume that the mass of the Earth is given by MeMeM_e, the mass of the Sun is given by MsMsM_s, and the Earth-Sun distance is given by resresr_es.

W= 0 J

You have just moved into a new apartment and are trying to arrange your bedroom. You would like to move your dresser of weight 3,500 NN across the carpet to a spot 5 mm away on the opposite wall. Hoping to just slide your dresser easily across the floor, you do not empty your clothes out of the drawers before trying to move it. You push with all your might but cannot move the dresser before becoming completely exhausted. How much work do you do on the dresser?

W= 0 J

A box of mass mmm is sliding down a frictionless plane that is inclined at an angle ϕϕphi above the horizontal, as shown in the figure (Figure 2). What is the work done on the box by the force due to gravity www, if the box moves a distance ddd?

W=wdcos(90−ϕ)

A ball is thrown straight upward. How does the sign of the work done by gravity while the ball is traveling upward compare with the sign of the work done by gravity while the ball is traveling downward?

Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward.

Is it possible for a system to have negative potential energy?

Yes, since the choice of the zero of potential energy is arbitrary.

Block 1 and block 2 have the same mass, mm, and are released from the top of two inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively. If the coefficient of friction is the same in both cases, which of the blocks is going faster when it reaches the bottom of its respective incline?

block 2 is faster

In a collision between two objects having unequal masses, how does magnitude of the impulse imparted to the lighter object by the heavier one compare with the magnitude of the impulse imparted to the heavier object by the lighter one?

both impulses receive same impulse

In a perfectly ELASTIC collision between two perfectly rigid objects

both the momentum and the kinetic energy of the system are conserved.

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back towards your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to MINIMIZE your speed on the skateboard?

catch the ball

As a tile falls from the roof of a building to the ground its momentum is conserved.

false

There must be equal amounts of mass on both side of the center of mass of an object.

false

A baseball is thrown vertically upward and feels no air resistance. As it is rising

its momentum is not conserved, but its mechanical energy is conserved.

A box of mass mm is pressed against (but is not attached to) an ideal spring of force constant kk and negligible mass, compressing the spring a distance xx. After it is released, the box slides up a frictionless incline as shown in the figure and eventually stops. If we repeat this experiment but instead compress the spring a distance of 2xx

just as it moves free of the spring, the box will be traveling twice as fast as before.

A ball drops some distance and loses 30 J of gravitational potential energy. Do NOT ignore air resistance. How much kinetic energy did the ball gain?

less than 30 J

When a constant force acts on an object, what does the object's change in momentum depend upon?

magnitude of force, time interval during which force acts, change in velocity of the object, mass of object

On a smooth horizontal floor, an object slides into a spring which is attached to another mass that is initially stationary. When the spring is most compressed, both objects are moving at the same speed. Ignoring friction, what is conserved during this interaction?

momentum and mechanical energy

A ball drops some distance and gains 30 J of kinetic energy. Do NOT ignore air resistance. How much gravitational potential energy did the ball lose?

more than 30 J

A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____.

negative

A small glider is coasting horizontally when suddenly a very heavy piece of cargo falls out of the bottom of the plane. You can neglect air resistance. Just after the cargo has fallen out

neither the cargo nor the plane change speed.

A block of mass mmm is pushed up against a spring with spring constant kkk until the spring has been compressed a distance xxx from equilibrium. What is the work done on the block by the spring? W=kx2 W=kx2 W=−kx2 W=−kx2 W=0 None of these.

none of these

Two objects, one of mass mm and the other of mass 2mm, are dropped from the top of a building. When they hit the ground

the heavier one will have twice the kinetic energy of the lighter one.

A shell that is initially at rest explodes into two fragments, one fragment 25 times heavier than the other. If any gas from the explosion has negligible mass, then

the kinetic energy change of the lighter fragment is 25 times as great as the kinetic energy change of the heavier fragment the momentum change of the lighter fragment is exactly the same as the momentum change of the heavier fragment.

A 1.0-kg block and a 2.0-kg block are pressed together on a horizontal frictionless surface with a compressed very light spring between them. They are not attached to the spring. After they are released and have both moved free of the spring

the lighter block will have more kinetic energy than the heavier block.

A box of mass mm is pressed against (but is not attached to) an ideal spring of force constant kk and negligible mass, compressing the spring a distance x. After it is released, the box slides up a frictionless incline as shown in the figure and eventually stops. If we repeat this experiment with a box of mass 2m

the lighter box will go twice as high up the incline as the heavier box.

In an INELASTIC collision between two objects

the momentum of the system is conserved but the kinetic energy of the system is not conserved.

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____.

the object's final speed was the same as its initial speed

Consider a plot of the displacement (xx) as a function of the applied force (FF) for an ideal elastic spring. The slope of the curve would be

the reciprocal of the spring constant.

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____.

the same magnitude and sign

A 3.00-kg ball swings rapidly in a complete vertical circle of radius 2.00 m by a light string that is fixed at one end. The ball moves so fast that the string is always taut and perpendicular to the velocity of the ball. As the ball swings from its lowest point to its highest point

the work done on it by gravity is -118 J and the work done on it by the tension in the string is zero.

If a force always acts perpendicular to an object's direction of motion, that force cannot change the object's kinetic energy.

true

Two objects are moving at equal speed along a level, frictionless surface. The second object has twice the mass of the first object. They both slide up the same frictionless incline plane. Which object rises to a greater height?

two objects rise to the same height

Swimmers at a water park have a choice of two frictionless water slides as shown in the figure. Although both slides drop over the same height, hh, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1v1 of a swimmer reaching the end of slide 1 compares with v2v2, the speed of a swimmer reaching the end of slide 2?

v1=v2

Suppose that we repeat the experiment in the video, but this time (1) the loop's diameter is twice that of the original loop and (2) the ball's starting position is twice as high above the table as that in the video. The initial height is sufficiently high as to allow the ball to travel all the way around the loop. How will the ball's speed at the top of the loop compare with the speed at the top of the loop in the video (v0v0)? Assume that we can ignore friction, and use the table as the level of zero potential energy.

√2v0