Physics: Energy, Momentum, and Work

An object's gravitational potential energy is directly related to all of the following EXCEPT a. its speed. b. its mass. c. the acceleration due to gravity. d. its height relative to a reference level

its speed

The unit of work is the a. meter. b. second. c. newton. d. joule. e. watt.

joule

An elastic collision is one in which a. kinetic energy before the collision is greater than kinetic energy after the collision. b. kinetic energy before the collision equals kinetic energy after the collision. c. kinetic energy after the collision is zero. d. kinetic energy before the collision is less than kinetic energy after the collision

kinetic energy before the collision equals kinetic energy after the collision

An inelastic collision is one in which a. kinetic energy after the collision is zero. b. kinetic energy before the collision is greater than kinetic energy after the collision. c. kinetic energy before the collision equals kinetic energy after the collision. d. kinetic energy before the collision is less than kinetic energy after the collision.

kinetic energy before the collision is greater than kinetic energy after the collision.

A superelastic collision is one in which a. kinetic energy before the collision equals kinetic energy after the collision. b. kinetic energy after the collision is zero. c. kinetic energy before the collision is less than kinetic energy after the collision. d. kinetic energy before the collision is greater than kinetic energy after the collision.

kinetic energy before the collision is less than kinetic energy after the collision.

gravitational potential energy

Potential energy that depends on the height of an object

Power

the rate at which work is done

If no friction acts on a diver during a dive, then which of the following statements is true? a. The total mechanical energy of the system increases. b. Potential energy can be converted into kinetic energy but not vice versa. c. (KE+ PE)beginning = (KE + PE)end d. all of the above

(KE+ PE)beginning = (KE + PE)end

How much work is done on a 60-N box of books that you carry horizontally across a 6-m room? a. 60 J b. 360 J c. 0 J d. 6 J e. 10 J

0 J

A 1-N apple falls to the ground. The apple hits the ground with an impact force of a. 1 N. b. Not enough information to say c. 4 N. d. 2 N. e. 9.8 N.

1 N

How much work is done on a 20-N crate that you lift 2 m? a. 40 J b. 20 J c. 0 J d. 1 J e. 2 J

40 J

How much power is expended if you lift a 60 N crate 10 meters in 1 second? a. 6 W b. 10 W c. 0 W d. 600 W e. 60 W

600 W

An arrow in a bow has 70 J of potential energy. Assuming no loss of energy to heat, how much kinetic energy will it have after it has been shot? a. 50 J b. 0 J c. 35 J d. 70 J e. 140 J

70 J

How much power is required to do 40 J of work on an object in 5 seconds? a. 8 W b. 200 W c. 40 W d. 0 W e. 5 W

8 W

isolated system

A system that can exchange neither energy nor matter with its surroundings.

Which of the following has the greatest momentum? a. a hare with a mass of 2.7 kg moving at a velocity of 7.5 m/s b. a tortoise with a mass of 275 kg moving at a velocity of 0.55 m/s c. a turtle with a mass of 91 kg moving at a velocity of 1.4 m/s d. a roadrunner with a mass of 1.8 kg moving at a velocity of 6.7 m/s

A tortoise with a mass of 275 kg moving at a velocity of 0.55 m/s

According to the conservation of mechanical energy, the kinetic energy before plus the kinetic energy after equals the potential energy before plus the potential energy after. True False

False

Energy cannot be changed from one variety to another. True False

False

Gravitation always does negative work. True False

False

If several forces are exerted on a system, calculate the work done by each force, then multiply the results. True False

False

Mechanical energy is the difference between kinetic energy and gravitational potential energy. True False

False

Power equals work multiplied by time. True False

False

Rest energy is the energy a body has due to its position at rest. True False

False

work

Force exerted on an object that causes it to move

thermal energy

Heat energy

equation for kinetic energy

KE=1/2mv^2

mechanical energy

Kinetic or potential energy associated with the motion or position of an object

Equation for power

P=W/t

equation for potential energy

PE=mgh

Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour? a. The small truck b. The large truck c. Both have the same momentum.

The large truck

When comparing the momentum of two moving objects, which of the following is correct? a. The less massive object will have less momentum if the velocities are the same. b. The more massive object will have less momentum if the velocities are the same. c. The more massive object will have less momentum if its velocity is greater. d. The object with the higher velocity will have less momentum if the masses are equal.

The less massive object will have less momentum if the velocities are the same.

Momentum

The product of an object's mass and velocity

The change in an object's momentum is equal to a. the product of the force applied to the object and the time interval. b. the time interval divided by the net external force. c. the product of the mass of the object and the time interval. d. the net external force divided by the time interval.

The product of the force applied to the object and the time interval.

The law of conservation of momentum states that a. the total momentum of all objects interacting with one another is zero. b. the total initial momentum of all objects interacting with one another does not equal the total final momentum. c. the total momentum of all objects interacting with one another remains constant regardless of the nature of the forces between the objects. d. the total initial momentum of all objects interacting with one another usually equals the total final momentum.

The total momentum of all objects interacting with one another remains constant regardless of the nature of the forces of the objects

work-energy theorem

The work done on an object equals the change in kinetic energy of the object

A stretched bow and a compressed rubber ball both possess elastic potential energy. True False

True

Gravitational potential energy is proportional to both mass and height above a reference level. True False

True

In a closed system, no objects enter or leave the system. True False

True

Power can also be written as force times velocity. True False

True

When there is an angle between the force and the displacement, W = F d cos θ. True False

True

If you lift two loads up one story, how much work do you do compared to lifting just one load up one story? a. One quarter as much b. The same amount c. One half as much d. Four times as much e. Twice as much

Twice as much

Work (Angle Between Force and Displacement)

W= Fdcos(theta)

equation for work

W=Fd

closed system

a system in which matter and energy exchanges do not occur across boundaries

A car traveling along the highway needs a certain amount of force exerted on it to stop. More stopping force may be required when the car has a. less stopping distance. b. more momentum. c. more mass. d. all of the above e. none of the above

all of the above

If the momentum of an object changes and its mass remains constant, a. it is accelerating (or decelerating). b. there is a force acting on it. c. its velocity is changing. d. all of the above e. none of the above

all of the above

The force of an apple hitting the ground depends upon a. the speed of the apple just before it hits. b. the time of impact with the ground. c. whether or not the apple bounces. d. air resistance on the apple as it falls. e. all of the above

all of the above

Which of the following is an example of an object with elastic potential energy? a. a wind-up toy that has been wound up b. a compressed basketball c. a stretched rubber band d. all of the above

all of the above

Which of the following statements is true according to the law of conservation of energy? a. Energy cannot be created. b. Energy cannot be destroyed. c. Energy can be converted from one form to another. d. all of the above

all of the above

Energy is changed from one form to another with no net loss or gain. a. Sometimes true b. Always true c. Always false

always true

impulse

change in momentum

A 75 kg person walking around a corner bumped into an 80 kg person who was running around the same corner. The momentum of the 80 kg person a. was conserved. b. remained the same. c. decreased. d. increased.

decreased

Two billiard balls collide and bounce off. Identify the type of collision. a. nearly elastic b. elastic c. perfectly inelastic d. inelastic

elastic

kinetic energy

energy of motion

In physics, work is defined as a. force divided by time. b. force times distance. c. distance divided by time. d. force divided by distance. e. force times time.

force times distance

If Nellie Newton pushes an object with twice the force for twice the distance, she does a. the same work. b. eight times the work. c. twice the work. d. four times the work.

four times the work

The reason padded dashboards are used in cars is that they a. decrease the impulse in a collision. b. look nice and feel good. c. decrease the momentum of a collision. d. increase the force of impact in a collision. e. increase the time of impact in a collision.

increase the time of impact in a collision

Potential energy is the energy an object has because of its a. density. b. temperature. c. location. d. size. e. speed.

location

The impulse experienced by a body is equivalent to the body's change in a. force. b. kinetic energy. c. velocity. d. momentum.

momentum

Equation for momentum

p=mv

Two balls of dough collide and stick together. Identify the type of collision. a. nearly elastic b. elastic c. perfectly inelastic d. inelastic

perfectly inelastic

Which of the following energy forms is associated with an object due to its position? a. kinetic energy b. potential energy c. total energy d. positional energy

potential energy

Impulse-Momentum Theorem

states that the impulse on an object equals the object's final momentum minus the object's initial momentum

elastic potential energy

the energy of stretched or compressed objects

Law of Conservation of Energy

the law that states that energy cannot be created or destroyed but can be changed from one form to another

reference level

the position where gravitational potential energy is defined as zero

The amount of potential energy possessed by an elevated object is equal to a. the force needed to lift it. b. the power used to lift it. c. the distance it is lifted. d. the value of the acceleration due to gravity. e. the work done in lifting it.

the work done in lifting it

The amount of potential energy possessed by an elevated object is equal to a. the work done in lifting it. b. the force needed to lift it. c. the value of the acceleration due to gravity. d. the distance it is lifted. e. the power used to lift it.

the work done in lifting it

The unit of power is the a. second. b. meter. c. watt. d. newton. e. joule.

watt

Power is defined as the a. distance divided by the time taken to move that distance. b. force on an object times the distance the object moves. c. work done times the time taken to do that work. d. work done on an object divided by the time taken to do the work. e. force on an object divided by the time the force acts.

work done on an object divided by the time taken to do the work