Deck 7: Energy

Question 1

One kilowatt-hour represents

A)1 N.
B)60 N/s.
C)60,000 W.
D)3.6 million joules.
E)none of these

Answer 1

3.6 million joules.

Question 2

Which task requires more work?

A)lifting the 50-kg sack 2 meters
B)lifting the 25-kg sack 4 meters
C)both require the same
D)need more information

Answer 2

both require the same

Question 3

A toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed using 1000 J of work, is

A)20 W.
B)50 W.
C)100 W.
D)1000 W.
E)20,000 W.

Answer 3

50 W.

Question 4

The work done in pushing a TV set a distance of 2 m with an average force of 20 N is

A)2 J.
B)10 J.
C)20 J.
D)40 J.
E)800 J.

Question 5

The work you do when pushing a shopping cart twice as far while applying twice the force is

A)half as much.
B)twice as much.
C)four times as much.
D)the same amount.

Question 6

The power required to exert 4-N force over 3 meters in 2 seconds is

A)4 W.
B)6 W.
C)8 W.
D)12 W.
E)none of the above

Question 7

Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is

A)twice as much as the 25-kg sack.
B)half as much as the 25-kg sack.
C)the same.
D)need more information

Question 8

The work you do when pushing a shopping cart a given distance while applying twice as much force is

A)half as much.
B)twice as much.
C)four times as much.
D)the same amount.

Question 9

The work you do when pushing a shopping cart twice as far while applying the same force is

A)half as much.
B)twice as much.
C)four times as much.
D)the same amount.

Question 10

If you do work on a skateboard loaded with friends in one-third the usual time, you expend

A)one third as much power.
B)the usual power.
C)three times the usual power.
D)need more information.

Question 11

When a drawn bow of potential energy 40 J is fired, the arrow will ideally have a kinetic energy

A)less than 40 J.
B)more than 40 J.
C)of 40 J.

Question 12

The power expended doing 100 J of work in 50 s is

A)1/2 W.
B)2 W.
C)4 W.
D)50 W.
E)5,000 W.

Question 13

No work is done by gravity on a bowling ball that rolls along a bowling alley because

A)no force acts on the ball.
B)little distance is covered by the ball.
C)the force on the ball is at right angles to the ball's motion.
D)the ball's speed remains constant.

Question 14

An object has gravitational potential energy due to its

A)speed.
B)acceleration.
C)momentum.
D)location.
E)none of the above

Question 15

The unit kilowatt-hour is a unit of

A)energy.
B)momentum.
C)power.
D)time.

Question 16

A 1000-kg car and a 2000-kg car are hoisted to the same height. Raising the more massive car requires

A)less work.
B)as much work.
C)twice as much work.
D)four times as much work.
E)more than four times as much work.

Question 17

The center of a long uniform log is raised to shoulder level while the other end is on the ground. If instead, the end of the log is raised to shoulder level, the work required is

A)half.
B)the same.
C)twice.

Question 18

A crate of grapes lifted 10 meters gains 200 J of potential energy. If the same crate is instead lifted 20 meters, its gain in potential energy is

A)half as much.
B)the same.
C)twice as much.
D)four times as much.
E)more than four times as much.

Question 19

The amount of work done on a heavy box carried by Nellie across a room at a constant speed

A)depends on the weight of the box.
B)depends on the distance walked.
C)depends on both weight of the box and distance walked.
D)is none.
E)none of the above

Question 20

Relative to an initial height, an object raised twice as high has a gravitational potential energy

A)half as much
B)twice as much.
C)four times as much.
D)need more information

Question 21

When Joshua brakes his speeding bicycle to a stop, kinetic energy is transformed to

A)potential energy.
B)energy of motion.
C)energy of rest.
D)heat.

Question 22

Two identical particles move toward each other, one twice as fast as the other. Just before they collide, one has a kinetic energy of 25 J and the other 50 J. At this instant their total kinetic energy is

A)25 J.
B)50 J.
C)75 J.
D)none of the above
E)need more information

Question 23

Which has greater kinetic energy?

A)a car traveling at 30 km/hr
B)a car of half the mass traveling at 60 km/hr
C)both the same
D)need more information

Question 24

Danny Diver weighs 500 N and steps off a diving board 10 m above the water. Danny hits the water with kinetic energy of

A)10 J.
B)500 J.
C)510 J.
D)5000 J.
E)more than 5000 J.

Question 25

A melon is tossed straight upward with 100 J of kinetic energy. If air resistance is negligible the melon will return to its initial level with a kinetic energy of

A)less than 100 J.
B)more than 100 J.
C)100 J.
D)need more information

Question 26

An object that has kinetic energy must be

A)moving.
B)falling.
C)at an elevated position.
D)at rest.
E)none of the above

Question 27

A bicycle that travels twice as fast as another when braking to a stop will skid

A)twice as far.
B)four times as far.
C)eight times as far
D)sixteen times as far.
E)depends on the bike's mass

Question 28

Two identical golf carts move at different speeds. The faster cart has twice the speed and therefore has

A)twice the kinetic energy.
B)four times the kinetic energy.
C)eight times the kinetic energy.
D)none of the above

Question 29

A motorcycle moving at 50 km/h skids 10 m with locked brakes. How far will it skid with locked brakes when traveling at 150 km/h?

A)10 m
B)30 m
C)50 m
D)90 m

Question 30

A bicycle that travels four as fast as another when braking to a stop will skid

A)twice as far.
B)four times as far.
C)eight times as far
D)sixteen times as far.
E)depends on the mass of the bike

Question 31

If a Ping-Pong ball and a golf ball both move in the same direction with the same amount of kinetic energy, the speed of the Ping-Pong ball must be

A)less than the golf ball.
B)more than the golf ball.
C)both the same
D)need more information

Question 32

Neglecting air resistance, Sammy Smarts on a high ladder releases a ball that strikes the ground with 100 J of kinetic energy. If he were to instead throw the ball straight upward, it will soon reach the ground with a kinetic energy of

A)less than 100 J.
B)100 J.
C)more than 100 J.

Question 33

About 40 J is required to push a crate 4 m across a floor. If the push is in the same direction as the motion of the crate, the force on the crate is about

A)4 N.
B)10 N.
C)40 N.
D)160 N.

Question 34

A 2-kg ball is held 4 m above the ground. Relative to the ground its potential energy is

A)6 J.
B)8 J.
C)32 J.
D)80 J.
E)more than 80 J.

Question 35

A cannonball has more kinetic energy than the recoiling cannon from which it is fired because the force on the ball

A)is more concentrated.
B)meets less resistance than the cannon on the ground.
C)acts over a longer distance.

Question 36

The ram of a pile driver drops onto the top of an iron beam, driving it partway into the ground. The distance that the beam sinks into the ground depends on the

A)initial height of the ram.
B)initial potential energy of the ram.
C)kinetic energy of the ram when it first hits the beam.
D)all of the above

Question 37

A clerk can lift cylindrical packages 1 meter vertically, or can roll them up a 2-meter-long ramp to the same elevation. With the ramp, the applied force required is about

A)half as much.
B)the same.
C)twice as much.
D)four times as much.

Question 38

A feather and a coin dropped in a vacuum fall with equal

A)forces due to gravity.
B)accelerations.
C)kinetic energies.
D)none of these

Question 39

A melon is projected into the air with 100 J of kinetic energy in the presence of air resistance. When it returns to its initial level its kinetic energy is

A)less than 100 J.
B)more than 100 J.
C)100 J.
D)need more information

Question 40

A 2-kg box of taffy candy has 40 J of potential energy relative to the ground. Its height above the ground is

A)1 m.
B)2 m.
C)3 m.
D)4 m.
E)none of the above

Question 41

A 2500-N pile-driver ram falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is

A)2,500 N.
B)25,000 N.
C)250,000 N.
D)2,500,000 N.

Question 42

Two identical arrows, one with twice the speed of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates

A)the same distance.
B)two times as far.
C)four times as far.
D)more than four times as far.
E)none of the above

Question 43

A common pulley acts similar to a

A)hydraulic press.
B)gear.
C)common lever.
D)tension producer.

Question 44

The bob of a simple pendulum has its maximum kinetic energy at the

A)top of its swing.
B)bottom of its swing.
C)midpoint between top and bottom.
D)at all points along its path of swing.

Question 45

If the speed of a bicycle is reduced to half before skidding to a stop, it will skid

A)one-eighth as far.
B)one-fourth as far.
C)one-half as far.
D)none of the above

Question 46

When properly used, a hydraulic press, like a wheel and axle, is capable of multiplying force input.

A)A true statement.
B)A false statement.
C)Yes, and in special cases, energy as well.

Question 47

A ball rolling down an incline has its maximum potential energy at

A)the top.
B)a quarter of the way down.
C)halfway down.
D)the bottom.

Question 48

Which requires the most amount of work by the brakes of a car?

A)slowing down from 100 km/h to 70 km/h
B)slowing down from 70 km/h to a stop
C)equal amounts for both

Question 49

A hydraulic press, like an inclined plane, is capable of increasing energy.

A)sometimes true
B)always false
C)always true
D)sometimes false

Question 50

A circus diver drops from a high pole into water far below. When he is halfway down

A)his potential energy is halved.
B)he has gained an amount of kinetic energy equal to half his initial potential energy.
C)his kinetic energy and potential energy are equal.
D)all of the above
E)none of the above

Question 51

A block of ice sliding down an incline has half its maximum kinetic energy

A)at the top.
B)at the bottom.
C)halfway down.
D)need more information

Question 52

Strictly speaking, more fuel is consumed by your car if the air conditioner, headlights, or even a radio is turned on. This statement is

A)false.
B)true only if the car's engine is running.
C)true.

Question 53

Two identical arrows, one with twice the kinetic energy of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates

A)the same distance.
B)twice as far.
C)four times as far.
D)more than four times as far.
E)none of the above

Question 54

After rolling halfway down an incline, a marble's kinetic energy is

A)less than its potential energy.
B)greater than its potential energy.
C)the same as its potential energy.

Question 55

A ball rolling down an incline has its maximum kinetic energy at

A)the top.
B)halfway down.
C)three-quarters of the way down.
D)the bottom.

Question 56

A light aluminum ball and a heavy lead ball of the same size roll down an incline. When they are halfway down the incline, they will have identical

A)kinetic energies.
B)potential energies.
C)momentum.
D)inertias.
E)none of the above

Question 57

Although perpetual motion is the natural order of things in the universe

A)it follows that machines can operate and do work by perpetual motion.
B)no perpetual-motion device that multiplies energy exists.
C)both of these are false statements

Question 58

Acrobat Bart at the circus drops vertically onto the end of a see-saw, with his partner Art equidistant from the fulcrum at the other end. Art is propelled straight upward a distance twice that of Bart's dropping distance. Neglecting inefficiencies we see

A)the masses of Art and Bart are equal.
B)Art has half the mass of Bart.
C)need more information

Question 59

A 1-kg ball dropped from 2 m rebounds only 1.5 m after hitting the ground. The amount of energy converted to heat is about

A)0.5 J.
B)1.0 J.
C)1.5 J.
D)2.0 J.
E)more than 2.0 J.

Question 60

When wind encounters a wind turbine that produces energy, wind speed on the downside of the blades is

A)slowed.
B)speeded up.
C)not affected.

Question 61

A hydraulic jack is used to lift objects such as automobiles. If the input force is 200 N over a distance of 1 meter, the output force over a distance of 0.1 meter is ideally

A)200 N.
B)500 N.
C)1000 N.
D)2000 N.
E)none of the above

Question 62

A moving object has

A)speed.
B)velocity.
C)momentum.
D)energy.
E)all of these

Question 63

A jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J. The efficiency of the jack system is

A)10%.
B)20%.
C)50%.
D)80%.
E)need more information

Question 64

A machine that promises more energy output than input is

A)a fantasy.
B)commonplace in today's technology.
C)a long-shot worth investing in.

Question 65

A miracle car with a 100% efficient engine burns fuel having a 40-megajoules-per-liter energy content. If air drag and overall frictional forces at highway speeds totals 1000 N, what distance per liter can be achieved on the highway?

A)30 km
B)40 km
C)50 km
D)more than 50 km
E)need more information

Question 66

Impulse involves the time that a force acts, whereas work involves the

A)distance that a force acts.
B)time and distance that a force acts.
C)acceleration that a force produces.

Question 67

A primary difference between momentum and kinetic energy is

A)momenta can cancel; kinetic energy cannot.
B)kinetic energy can cancel; momenta cannot.
C)either of the above depending on circumstances
D)none of the above

Question 68

Solar power is commonly used to produce

A)heat.
B)electricity.
C)both of these

Question 69

Earth's primary energy source is

A)the Sun.
B)fossil fuel.
C)electricity.
D)geothermal.

Question 70

A hydraulic press has its input piston depressed 20 centimeters while the output piston is raised 1 centimeter. A 1-newton input can lift a load of

A)1 N.
B)10 N.
C)15 N.
D)20 N.
E)none of the above

Question 71

If an all-electric car has kinetic energy, then it also must have

A)impulse.
B)momentum.
C)acceleration.
D)force.
E)none of the above

Question 72

A car's engine is 20% efficient. When cruising, the car encounters an average retarding force of 1000 N. If the energy content of fuel is 40 megajoules per liter, how many kilometers per liter does the car achieve?

A)8
B)10
C)12
D)14
E)none of the above

Question 73

Hydrogen, like electricity, is

A)an energy source.
B)not an energy source.
C)a source of both thermal and electric power.

Question 74

The most concentrated form of energy is

A)wind.
B)fossil fuel.
C)geothermal.
D)nuclear.

Question 75

A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is

A)10%.
B)50%.
C)90%.
D)110%.
E)none of the above

Question 76

The exhaust product from a hydrogen fuel cell is

A)carbon dioxide.
B)methane.
C)pure water.
D)nitric acid.

Question 77

If the speed of a motor scooter doubles, which of the following also doubles?

A)momentum
B)kinetic energy
C)acceleration
D)all of the above

Question 78

Phil applies 100 N to a pulley system and raises a load one-tenth of his downward pull. Ideally, the weight of the load is

A)100 N.
B)1000 N.
C)10,000 N.
D)more than 10,000 N

Question 79

Which of these is not a form of solar energy?

A)wind energy
B)fossil fuel energy
C)geothermal energy
D)hydroelectric power

Question 80

Hydro and wind power are indirect forms of

A)solar energy.
B)fossil fuels deep down.
C)nuclear energy in Earth's interior.
D)none of the above