homework #3 and Ch. 3 PPT Q's

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

A) 40 J

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

A) false

An object may have potential energy because of its A) location. B) speed. C) momentum. D) acceleration. E) none of the above

A) location

When a cannon fires a cannonball at a given speed, the smaller recoil speed of the cannon is due to different A) masses. B) times. C) forces. D) momenta.

A) masses

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

A) on the wall

When a simple machine multiplies force, it decreases A) potential energy. B) distance moved. C) both D) neither

B) distance moved

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) doubled. C) zero. D) quadrupled.

B) doubled

A simple machine CANNOT multiply A) distance. B) energy. C) force. D) none of the above

B) energy

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

B) twice as much work

When you push an object a certain distance while applying twice the force, you do A) four times as much work. B) twice as much work. C) the same amount of work.

B) twice as much work

When the speed of an object is doubled, its momentum A. remains unchanged in accord with the conservation of momentum. B. doubles. C. quadruples. D. decreases.

B. doubles

Freight Car A is moving toward identical Freight Car B that is at rest. When they collide, both freight cars couple together. Compared with the initial speed of Freight Car A, the speed of the coupled freight cars is A. the same. B. half. C. twice. D. None of the above.

B. half

A cannonball shot from a cannon with a long barrel will emerge with greater speed, because the cannonball receives a greater A. average force. B. impulse. C. Both of the above. D. Neither of the above.

B. impulse

In an ideal pulley system, a woman lifts a 100-N crate by pulling a rope downward with a force of 25 N. For every one-meter length of rope she pulls downward, the crate rises A. 50 centimeters. B. 45 centimeters. C. 25 centimeters. D. None of the above.

C. 25 centimeters

A job can be done slowly or quickly. Both may require the same amount of work, but different amounts of A. energy. B. momentum. C. power. D. impulse.

C. power

The work done in braking a moving car to a stop is the force of tire friction × stopping distance. If the initial speed of the car is doubled, the stopping distance is A. actually less. B. about the same. C. twice. D. None of the above.

C. twice

A heavy truck and a small truck roll down a hill. Neglecting friction, at the bottom of the hill the heavy truck has greater A) acceleration. B) speed. C) momentum. D) all of the above E) none of the above

C) momentum

In order to catch a fast-moving softball with your bare hand, you extend your hand forward just before the catch and then let the ball ride backward with your hand. Doing this reduces the catching force because the A) time of catch is increased. B) relative velocity is less. C) relative velocity is more. D) time of the catch is decreased. E) none of the above

A) time of catch is increased

The distinction between impulse and force involves the A) time the force acts. B) mass and its effect on resisting a change in momentum. C) distance the force acts. D) difference between acceleration and velocity.

A) time the force acts

A certain machine is 30% efficient. This means the machine will convert A. 30% of the energy input to useful work—70% of the energy input will be wasted. B. 70% of the energy input to useful work—30% of the energy input will be wasted. C. As strange as it may seem, both of the above. D. None of the above.

A. 30% of the energy input to useful work-70% of the energy input

When a dish falls, will the change in momentum be less if it lands on a carpet than if it lands on a hard floor? (Careful!) A. No, both are the same. B. Yes, less if it lands on the carpet. C. No, less if it lands on a hard floor. D. No, more if it lands on a hard floor.

A. No, both are the same

Does a car hoisted for repairs in a service station have increased potential energy relative to the floor? A. Yes. B. No. C. Sometimes. D. Not enough information.

A. Yes

Must a car with momentum have kinetic energy? A. Yes, due to motion alone. B. Yes, when motion is nonaccelerated. C. Yes, because speed is a scalar and velocity is a vector quantity. D. No.

A. Yes, due to motion alone

If you push against a stationary brick wall for several minutes, you do no work A. on the wall. B. at all. C. Both of the above. D. None of the above.

A. on the wall

Work is done in lifting a barbell. How much work is done in lifting a twice-as-heavy barbell the same distance? A. Twice as much. B. Half as much. C. The same. D. Depends on the speed of the lift.

A. twice as much

A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force to stop the car, the force needed to stop the truck is A) smaller. B) greater. C) the same.

B) greater

A cannonball fired from a long- barrel cannon will have a greater muzzle velocity because the cannonball receives a greater A) force. B) impulse. C) both D) neither

B) impulse

When you are in the way of a fast- moving object and canʹ t get escape, you will suffer a smaller force if the collision time is A) short. B) long. C) the same way either way.

B) long

Compared with falling on a wooden floor, a wine glass may not break when it falls on a carpeted floor because of A) lesser impulse in stopping. B) longer time to stop. C) both D) neither

B) longer time to stop

If you do work on an object in half the time, your power output is A) half. B) twice. C) the same.

B) twice

When the force that produces an impulse acts for twice as much time, the impulse is A. not changed. B. increased by two times. C. increased by four times. D. decreased by half.

B. increased by two times

You do work when pushing a cart. If you push the cart twice as far with the same constant force, then the work you do is A. less than twice as much. B. twice as much. C. more than twice as much. D. zero.

B. twice as much

It is correct to say that impulse is equal to A) momentum. B) the force multiplied by the distance the force acts. C) the change in momentum. D) all of the above E) none of the above

C) the change in momentum

A fast-moving car hitting a haystack or hitting a cement wall produces vastly different results. Both experience A. the same change in momentum. B. the same impulse. C. the same force. D. A and B.

D. A and B

Consider a problem that asks for the distance a fast moving crate slides across a factory floor in coming to a stop. The most useful equation for solving this problem is A. F = ma. B. Ft = ∆mv. C. KE = 1/2mv2. D. Fd = ∆1/2mv2.

D. Fd = ∆1/2mv2.

A moving object has A. momentum. B. energy. C. speed. D. All of the above.

D. all of the above

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

E) all of the above