Physics Chapter 4

You lift a barbell a certain distance from the floor. If you lift it twice as high, its potential energy is (A) twice as great (B) the same (C) half as great (D) none of the above

A

A ball is moving at 4 m/s and has a momentum of 48 kg×m/s. What is the ball's mass? (A) 12 kg (B) 192 kg (C) 4 kg (D) 48 kg (E) none of the above

A

A boxer rides with the punch so as to reduce (A) force. (B) speed. (C) momentum. (D) impulse.

A

Can a machine multiply input energy? (A) No (B) Yes

A

For the same force, which cannon impacts the greater speed to a cannonball - a long cannon or a short one? (A) The long cannon (B) The short cannon (C) Both cannons impact the same speed to a cannonball

A

How does impulse differ from force? (A) Force is a push or pull, while impulse is the product of force and time. (B) Force is a push or pull, while impulse is the product of force and distance. (C) Force is a push or pull, while impulse is the ratio of force to time. (D) Impulse is a push or pull, while force is the product of impulse and time.

A

If you push an object twice as far while applying the same force, you do (A) twice as much work. (B) four times as much work. (C) the same amount of work.

A

If you push for an hour against a stationary wall, no work is done (A) on the wall. (B) at all. (C) both of the above (D) none of the above

A

In a simple machine, how much work is done when an input of 10 N acts over a distance of 5 m? (A) 50 J. (B) 5 J. (C) 10 J. (D) 15 J.

A

In what unit POWER is measured? (A) In Watt (B) In m/s (C) In Joule (D) In Newton

A

Momentum is conserved in (A) all collisions in which external forces don't affect motion. (B) only elastic collisions. (C) only inelastic collisions. (D) any kind of collision.

A

Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is (A) greater than that of the apple only if the apple bounces. (B) negligible compared to the momentum of the apple. (C) greater than that of the apple in all cases. (D) none of the above

A

The conservation of momentum is most closely related to (A) Newton's Third Law. (B) Newton's Second Law. (C) Newton's First Law.

A

True or false: One watt is the unit of power equivalent to 1 joule per second. (A) True (B) False

A

What do we call the quantity (Force) x (Distance)? (A) Work (B) Momentum (C) Power (D) Impulse

A

What does it mean to say that a quantity is conserved? (A) It means that the quantity remains unchanged in a process. (B) It means that the quantity equals zero. (C) It means that the quantity changes in a process. (D) None of the above.

A

A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground? (A) 40 J (B) 80 J (C) 60 J (D) 20 J (E) none of the above

B

A machine puts out 100 W of power for every 1000 W put into it. The efficiency of the machine is (A) 90 percent. (B) 10 percent. (C) 110 percent. (D) 50 percent. (E) none of the above

B

A woman lifts a box from the floor. She then moves with constant speed to the other side of the room, where she puts the box down. How much work does she do on the box while walking across the floor at constant speed? (A) more than 0 J (B) 0 J (C) not enough information given

B

An object is raised above the ground gaining a certain amount of potential energy. If the same object is raised twice as high, it gains (A) four times as much potential energy. (B) twice as much potential energy. (C) none of the above

B

An open freight car rolls friction-free along a horizontal track in a pouring rain that falls vertically. As water accumulates in the car, its speed (A) increases. (B) decreases. (C) doesn't change

B

Can a machine multiply input force? (A) No (B) Yes

B

Compared to a recoiling rifle, the bullet fired has a greater (A) momentum. (B) kinetic energy. (C) none of the above

B

Consider a baseball that is caught and thrown at the same speed. Which case requires the greatest impulse? (A) The baseball being thrown. (B) The baseball being caught and then thrown back. (C) The baseball being caught.

B

For which type of collision is momentum conserved? (A) Momentum is not conserved in elastic and inelastic collisions. (B) Momentum is conserved in both elastic and inelastic collisions. (C) Momentum is not conserved in elastic collisions and is conserved in inelastic collisions. (D) Momentum is conserved in elastic collisions and is not conserved in inelastic collisions.

B

How can a huge ship have an enormous momentum when it moves relatively slowly? (A) The ship has enormous momentum due to huge friction force. (B) The ship has enormous momentum due to huge mass. (C) The ship has enormous momentum due to huge acceleration. (D) None of the above.

B

If you exert 1 N for a distance of 1 m in 1 s, you will deliver a power of (A) 2 W. (B) 1 W. (C) 1/3 W. (D)3 W. (E) none of the above

B

In bungee jumping, the change in a jumper's kinetic energy equals the average force of the bungee cord multiplied by the stretching (A) time. (B) distance. (C) both of the above (D) none of the above

B

A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at (A) 1/2 m/s. (B) 0 m/s. (C) 1/3 m/s. (D) 1/6 m/s. (E) 1.5 m/s.

C

A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy of (A) less than 40 J. (B) more than 40 J. (C) 40 J.

C

A slowly moving ship has a large momentum because of its (A) tendency to drift toward a distant port. (B) low speed. (C) large mass. (D) usually straight-line direction.

C

Exert 100J in 50s, and your power output is (A) 14W (B) 12W (C) 2 W (D) 4 W

C

An object at rest may have (A) velocity. (B) momentum. (C) speed. (D) energy. (E) none of the above

D

Energy cannot be (A) transferred, transformed, or destroyed. (B) transformed. (C) transferred. (D) destroyed.

D

Two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. The faster arrow will penetrate (A) four times as far as the slower arrow. (B) the same distance as the slower arrow. (C) more than four times as far as the slower arrow. (D) twice as far as the slower arrow. (E) none of the above

D

What do we call the quantity force × distance? (A) Momentum (B) Impulse (C) Power (D) Work

D

A hydraulic press, like a simple level, properly arranged is capable of multiplying energy input. (A) always false (B) sometimes true

A

If you exert 100 J in 50 s, your power output is (A) 4 W. (B) 1/4 W. (C) 2 W. (D) more than 4 W. (E) 1/2 W.

C

If you push an object just as far while applying twice the force, you do (A) four times as much work. (B) the same amount of work. (C) twice as much work.

C

What is the definition of an elastic collision? (A) A collision in which the total momentum is not conserved. (B) A collision in which colliding objects are subjected by external forces. (C) A collision in which colliding objects rebound without lasting deformation or the generation of heat. (D) A collision in which the colliding objects become distorted, generate heat, and possibly stick together.

C

What is the law of energy conservation? (A) The energy of a system remains unchanged only if there are no external forces acting on the system. (B) The change in energy of the object equals the impulse acting on the object. (C) In the absence of external work input or output, the energy of a system remains unchanged. Energy cannot be created or destroyed. (D) In the absence of momentum, the energy of a system remains unchanged. Energy cannot be created or destroyed.

C

One end of a long uniform log is raised to shoulder level. An identical log is raised at its center to the same level. Raising the second log requires about (A) twice as much work. (B) the same amount of work. (C) more than twice as much work.

A

Suppose a miracle car has a 100 percent efficient engine and burns fuel that has a 40 MJ/L energy content. If the air drag and overall frictional forces on this car traveling at highway speeds is 1000 N, what is the overall limit in distance per liter it could be driven on the highway? (A) 40 km (B) more than 50 km (C) 30 km (D) 50 km (E) not enough information given

A

In what units are work and energy measured? (A) Work is measured in joules and energy is measured in watts. (B) Work and energy are measured in joules. (C) Work and energy are measured in watts. (D) Work is measured in watts and energy is measured in joules.

B

Is it possible to design a machine that has an efficiency greater than 100%? (A) No because a machine that has an efficiency greater than 100% uses more energy than it outputs, therefore, the machine destroys energy. It violates the law of energy conservation. (B) No because a machine that has an efficiency greater than 100% outputs more energy than it uses, therefore, the machine creates additional energy. It violates the law of energy conservation. (C) Yes because a machine that has an efficiency greater than 100% uses more energy than it outputs, therefore, a part of input energy is dissipated as heat. A machine can only transfer energy from one place to another or transform it from one form into another. (D) Yes because a machine that has an efficiency greater than 100% outputs more mechanical energy than it uses, therefore, the machine transforms energy from one form into another, for example, from chemical energy stored in gasoline into mechanical energy.

B

What is the law of energy conservation? (A) he energy of a system remains unchanged only if there are no external forces acting on the system. (B) In the absence of external work input or output, the energy of a system remains unchanged . Energy cannot be created or destroyed.

B

When you are traveling twice as fast your kinetic energy is increased (A) by three. (B) by four. (C) by two. (D) not at all.

B

For the same force, which cannon imparts the greater speed to a cannonball − a long cannon or a short one? (A) The short cannon. (B) Both cannons impart the same speed to a cannonball. (C) The long cannon.

C

Which has a greater momentum - a heavy truck at rest or a moving skateboard? (A) The moving skateboard. (B) Heavy truck at rest

A

What quantity does it change? (A) Acceleration (B) Energy (C) Momentum (D) Impulse

B

A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is (A) unchanged. (B) zero. (C) quadrupled. (D) doubled.

D

What quantity does work change? (A) Momentum (B) Acceleration (C) Impulse (D) Energy

D

When one does twice the work in twice the time, the power expended is (A) four times as much. (B) three times as much. (C) twice as much. (D) the same.

D

When you lift a load twice as high, the increase in potential energy is (A) the same. (B) three times as much. (C) four times. (D) twice as much.

D

A moving object has (A) momentum. (B) speed. (C) energy. (D) velocity. (E) all of the above

E

Which of the following has the largest momentum relative to the earth? (A) a tightrope walker crossing Niagara Falls (B) the Science building on campus (C) a dog running down the street (D) a Mack truck parked in a parking lot (E) a pickup truck speeding along a highway

E

Recoil is noticeable if we throw a heavy ball while standing on roller skates. If instead we go through the motions of throwing the ball but hold onto it, our net recoil will be (A) small, but noticeable. (B) zero. (C) the same as before.

B

The average momentum of a 70-kg runner who covers 400 m in 50 s is (A) 57 kg×m/s. (B) 560 kg×m/s. (C) 5490 kg×m/s. (D) 8.75 kg×m/s.

B

A cannon recoils from firing a cannonball. The speed of the cannon's recoil is small because the (A) cannon has more mass than the ball. (B) force against the cannon is smaller than against the ball. (C) momentum of the cannon is smaller. (D) momentum is mainly concentrated in the ball.

A

An object that has kinetic energy must be (A) moving. (B) at an elevated position. (C) at rest. (D) falling. (E) none of the above

A

Can a machine multiply input distance? (A) Yes (B) No

A

Consider a baseball that is caught and thrown at the same speed. Which case illustrates the greatest change in momentum? (A) The baseball being caught and then thrown back. (B) The baseball being caught. (C) The baseball being thrown.

A

What is (are) the way(s) in which the impulse exerted on something can be increased? (A) Two ways to increase impulse are to increase force or increase the time the force is exerted. (B) The way to increase impulse is to decrease mass. (C) Two ways to increase impulse are to increase force or decrease the time the force is exerted. (D) Two ways to increase impulse are to decrease force or decrease the time the force is exerted.

A

What is the definition of an inelastic collision? (A) A collision in which the colliding objects become distorted, generate heat, and possibly stick together. (B) A collision in which the total momentum is not conserved. (C) A collision in which colliding objects are subjected by external forces. (D) A collision in which colliding objects rebound without lasting deformation or the generation of heat.

A

Which has a greater momentum − a heavy truck at rest or a moving skateboard? (A) Heavy truck at rest. (B) Moving skateboard.

B

Can you produce a net impulse on a car by sitting inside and pushing on the dashboard? (A) No, because your push is external. To change the automobile's momentum, an external force must be applied. (B) Yes, because your push is external. To change the automobile's momentum, an external force must be applied. (C) No, because your push is internal. To change the automobile's momentum, an external force must be applied. (D) Yes, because your push is internal. To change the automobile's momentum, an internal force must be applied.

C

Consider massive gliders that slide friction-free along a horizontal air track. Glider A has a mass of 1 kg, a speed of 1 m/s, and collides with glider B, which has a mass of 5 kg and is at rest. If they stick upon collision, their speed after collision will be (A) 1 m/s. (B) 1/4 m/s. (C) 1/6 m/s. (D) 1/5 m/s. (E) none of the above

C

How many joules of energy are in 1 kWh? (A) 60 kJ (B) 1 J (C) 3.6MJ (D) 60 J (E) none of the above

C

The quantity called impulse can be measured by (A) how long the force acts compared to the amount of time. (B) the difference between force and time. (C) the product of force and time. (D) the addition of force and time.

C

When an increase in speed doubles the momentum of a moving body, its kinetic energy. (A) more than doubles (B) increases, but less than doubles (C) depends on factors not stated

A

When an increasing in speed doubles the momentum of moving body, its kinetic energy (A) more than doubles (B) doubles (C) increases, but less than doubles (D) depends on factors not stated

A

The work that is done when twice the load is lifted twice the distance is (A) twice as much. (B) four times as much. (C) the same. (D) three times as much.

B

Two objects, A and B, have the same size and shape, but A is twice as heavy as B. When they are dropped simultaneously from a tower, they reach the ground at the same time, but A has greater (A) speed. (B) acceleration. (C) momentum. (D) all of the above (E) none of the above

C

What is the source of energy that powers a hydroelectric power plant? (A) The kinetic energy of wind that carried evaporated water, which fell as rain and filled reservoirs (B) The energy of the chemical bonds of water molecules. (C) The sunlight that evaporated water that eventually falls as rain and fills the reservoir. (D) The thermal energy of the water behind dams.

C

When an object is lifted 10 m, it gains a certain amount of potential energy. If the same object is lifted 20 m, its potential energy gain is (A) the same. (B) more than four times as much. (C) twice as much. (D) less. (E) four times as much.

C

Which requires more work: lifting a 50-kg sack vertically 2 m or lifting a 25-kg sack vertically 4 m? (A) lifting the 25-kg sack (B) lifting the 50-kg sack (C) Both require the same amount of work.

C

A 1000-kg car and a 2000-kg car are hoisted the same distance in a gas station. Raising the more massive car requires (A) as much work. (B) more than four times as much work. (C) four times as much work. (D) twice as much work. (E) less work.

D

A 2-kg mass has 40 J of potential energy with respect to the ground. Approximately how far is it located above the ground? (A) 3 m (B) 1 m (C) 4 m (D) 2 m (E) none of the above

D

A TV set is pushed a distance of 2 m with a force of 20 N that is in the same direction as the set moves. How much work is done on the set? (A) 2 J (B) 80 J (C) 10 J (D) 40 J (E) 20 J

D

A boxer punches a sheet of paper in midair and brings it from rest up to a speed of 40 m/s in 0.05 s. If the mass of the paper is 0.01 kg, the force of impact on the paper is about (A) 0.08 N. (B) 80 N. (C) 0.8 N. (D) 8.0 N.

D

A car's engine is 20 percent efficient. When cruising, the car encounters an average retarding force of 1000 N. If the energy content of gasoline is 40 MJ/L, how many kilometers per liter does the car get? (A) 14 km/L (B) 10 km/L (C) 12 km/L (D) 8 km/L (E) none of the above

D

What does an object have when moving that it doesn't have when at rest? (A) energy (B) inertia (C) mass (D) momentum (E) none of the above

D