Deck 6: Conservation of Energy: You Cant Get Ahead

Question 1

The basic energy resource that fueled the "industrial revolution" was a form of

A) gravitational energy.
B) nuclear energy.
C) thermal energy.
D) radiant energy.
E) chemical energy.

Answer 1

chemical energy.

Question 2

Early human culture, involving villages and a sense of history, could best be described as a(n)

A) industrial culture.
B) hunting culture.
C) agri- culture.
D) scientific culture.
E) migratory culture.

Answer 2

agri- culture.

Question 3

A 75- watt lightbulb

A) consumes 75 joules of electric energy during every second.
B) creates 75 joules of thermal energy during every second.
C) creates 75 joules of radiant energy during every second.
D) creates a total of 75 joules of radiant energy during the entire lifetime of the bulb.
E) consumes a total of 75 joules of electric energy during the entire lifetime of the bulb.

Answer 3

consumes 75 joules of electric energy during every second.

Question 4

A low- power source of energy could put out a lot of work provided it

A) exerted a sufficiently strong force.
B) operated for a short time.
C) operated for a long time.
D) exerted its power over a very large distance.
E) Nonsense-- there is no way that a low- power source can put out a large amount of work.

Question 5

A block of ice slides freely [no air resistance, no friction] down a slippery slope. The block starts from rest at the top of the slope, where it has a vertical height of 4 m above the bottom of the slope and where it has a gravitational energy of 1000 J. At a quarter of the way down the slope, the block's kinetic energy is

A) 250 J.
B) 500 J.
C) 750 J.
D) 1000 J.
E) less than 250 J.

Question 6

Suppose you slowly, and at constant speed, lift a book weighing 12 N from the floor to a shelf 2 m above the floor. Neglect air resistance. While you are lifting, the net force on the book is

A) 12 N directed upward.
B) 12 N directed downward.
C) less than 12 N, by an amount that depends on the speed of lifting.
D) zero.
E) more than 12 N, by an amount that depends on the speed of lifting.

Question 7

Which of the following measures would help reduce the need for new electric power plants?

A) Energy storage methods at electric power plants.
B) More energy- efficient use of electricity.
C) "Time- of- day"pricing that charges more for electricity at the "peak" times.
D) All three of the above measures would help.
E) Both measures A and C would help, but not B.

Question 8

What physical quantity is measured in "watts"?

A) power
B) electric current
C) energy
D) force
E) voltage

Question 9

You run up a flight of stairs, and then you walk up a second, identical, flight of stairs. Compared with running up the first flight of stairs, in walking up the second flight your

A) work output is greater.
B) power output is smaller.
C) work output is smaller.
D) power output is greater.
E) None of the above.

Question 10

To what two quantities is work proportional?

A) acceleration and distance
B) force and speed
C) energy and distance
D) force and distance
E) power and distance

Question 11

Mortimer pushes against a wall with a force of 10 newtons for a time of 5 seconds. How much work does Mortimer do on the wall?

A) none
B) 50 J
C) 2 J
D) 5 J
E) 10 J

Question 12

The rate of doing work, or of transforming energy, can be measured in

A) Calories.
B) watts.
C) joules.
D) newtons.
E) kilowatt- hours.

Question 13

Which one of our 8 standard physical forms of energy is present in sunlight?

A) thermal
B) chemical
C) solar
D) kinetic
E) radiant

Question 14

Which of the following processes is an example of an energy transformation from chemical energy to gravitational energy?

A) a ball rolling downhill
B) lifting a book, with your hands, from the floor to a table top
C) using the water behind a dam to run an electric generator
D) burning coal to run an electric generator
E) striking [lighting] a match to warm up your hand

Question 15

Thousands of years ago, after humans began settling in villages, their settlements were energized by

A) radiant energy.
B) gravitational energy.
C) chemical energy.
D) nuclear energy.
E) thermal energy.

Question 16

Which of the following is an example of chemical energy?

A) the energy stored in firewood that has been gathered for burning
B) the energy stored in your body, that enables you to do work
C) Both of the above.
D) the energy in hot steam
E) the energy in a stretched rubber band

Question 17

How much work do you do when you lift a 3 N apple by 2 m during a time of 6 s?

A) 6 J
B) 1.5 J
C) 1 J
D) 18 J
E) 12 J

Question 18

Balloons expand when they are heated because

A) of the additional molecules in them.
B) the molecules inside are moving faster.
C) the molecules inside become more massive.
D) the molecules inside expand when they are heated.
E) Nonsense-- balloons don't expand when they are heated.

Question 19

The energy transformation that occurs during downhill skiing is

A) chem E ·kin E + therm E.
B) kin E ·grav E.
C) grav E ·kin E + therm E.
D) kin E ·grav E + therm E.
E) grav E ·chem E.

Question 20

A motionless object could have

A) kinetic energy.
B) elastic energy.
C) speed.
D) All of the above.
E) None of the above.

Question 21

What is one "kilowatt- hour" [kW · h]?

A) It is the force output of one kilowatt operating for one hour.
B) It is the power output of a one kilowatt device.
C) It is work done continuously for one hour.
D) It is the energy output of one kilowatt operating for one hour.
E) Actually, nobody knows what this term means.

Question 22

In its monthly bill, the electric company charges you primarily for

A) the number of cabbages you consume during the month.
B) the useful energy output that all your electric devices produce during the month.
C) the electric force you consume during the month.
D) the electric power you consume during the month.
E) the electric energy you consume during the month.

Question 23

A 10 kg meteor moves through outer space, far from all gravitational influences. How much work is done on the meteor during a 5 m segment of its path?

A) none
B) 20 J
C) 500 J
D) 2 J
E) 50 J

Question 24

Elizabeth lifts a book from the floor to the table. The energy transformation is

A) chemical ·gravitational.
B) electromagnetic ·gravitational.
C) gravitational ·chemical.
D) thermal ·gravitational.
E) chemical ·kinetic.

Question 25

The kilowatt is a measure of

A) energy.
B) power.
C) force.
D) speed.
E) sex appeal.

Question 26

A 100 W lightbulb has an energy efficiency of 5%. It is turned on for one minute. During this time, the visible radiant energy output of the lightbulb is

A) 6000 J.
B) 300 J.
C) 5700 J.
D) impossible to determine because we don't know the voltage.
E) impossible to determine because we don't know the power.

Question 27

You push your physics book across a table. The book weighs 8 N, you push with a steady 5 N force, and the force of friction against the book is 3 N. You push the book a distance of 2 m. The amount of work you do on the book is

A) 6 J.
B) 10 J.
C) zero.
D) 16 J.
E) impossible to tell without more information.

Question 28

"Time- of- day" pricing of electricity could help to

A) reduce total electric energy use by encouraging users to use less electric energy.
B) reduce the need for new power plants by encouraging users to use electric energy at less popular times.
C) reduce total electric energy use by encouraging users to use electric energy at less popular times.
D) reduce the nation's appetite for chocolate fudge.
E) reduce the need for new power plants by encouraging users to use less electric energy.

Question 29

Electric generating plants are usually rated in "megawatts". This is a unit of

A) force.
B) power.
C) energy.
D) work.
E) both energy and work.

Question 30

Suppose you slowly lift a book from the floor and put it on a table. Which of the following energy transformations best describes the overall process?

A) thermal to gravitational
B) kinetic to gravitational
C) kinetic to chemical
D) gravitational to chemical
E) chemical to gravitational

Question 31

Since 1 kilowatt equals 1000 watts, and 1 hour equals 3600 seconds, it follows that the kilowatt- hour is

A) an energy of 3.6 million joules.
B) a power of 3.6 million joules.
C) a power of 3.6 million watts.
D) an energy of 3.6 million watts.
E) None of the above.

Question 32

The earliest human culture, involving villages and a sense of history, developed

A) about one billion years ago.
B) about 1000 years ago.
C) a few million years ago.
D) 100,000 to 200,000 years ago.
E) about 10,000 years ago.

Question 33

Chemical energy is transformed into gravitational energy when

A) a leaf undergoes photosynthesis.
B) a car accelerates.
C) a block slides downhill.
D) a person walks uphill.
E) water evaporates.

Question 34

One joule is the same as one

A) newton- meter.
B) kilowatt- hour.
C) meter per second squared.
D) watt- meter.
E) newton- second.

Question 35

The energy conversion represented by an automobile speeding up along a level road is

A) chemical to kinetic.
B) chemical to gravitational.
C) gravitational to kinetic.
D) kinetic to chemical.
E) thermal to chemical.

Question 36

What is the main energy transformation (input and useful output) for a person speeding up while riding a bicycle?

A) elastic E ·kinetic E
B) chemical E ·kinetic E
C) thermal E ·kinetic E
D) chemical E ·elastic E
E) kinetic E ·chemical E

Question 37

A meteor having a mass of 1000 kg moves through outer space, far from all planets and stars and far from all gravitational influences, at a speed of 20 km/s (20,000 m/s). How much work is done on the meteor during a time interval of one second?

A) 20 J
B) 1000 J
C) 20 × 10⁶ J
D) 20 000 J
E) None of the above.

Question 38

An automobile travels at an unchanging speed of 80 km/hr on a straight level road. Which of the following best represents the overall energy process occurring here?

A) Kin E ·Chem E
B) Thermal E ·Chem E
C) Chem E ·Thermal E
D) Chem E ·Kin E

Question 39

The figure above shows a marble rolling freely back and forth along a curved track. The track is positioned vertically. At position A its gravitational energy is

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

Question 40

The type of energy that a swinging pendulum has at the low point of its swing is

A) thermal.
B) kinetic.
C) sexual.
D) elastic.
E) gravitational.

Question 41

The main energy transformation that occurs while an electric blender is mixing your orange juice is

A) chemical E ·thermal E.
B) electric E ·kinetic E.
C) thermal E ·kinetic E.
D) kinetic E ·electric E.
E) electric E ·chemical E.

Question 42

The figure above shows a marble rolling freely back and forth along a curved track. The track is positioned vertically. Assuming no friction and no air resistance, the total energy of the marble

A) decreases when the marble rolls from A to B.
B) increases when the marble rolls from A to B.
C) remains the same when the marble rolls from A to B.

Question 43

A particular lightbulb produces 8 J of thermal energy while producing 2 J of radiant energy, and this is its entire energy output during this time. How energy- efficient is this bulb [as a producer of light]?

A) 80%
B) 500%
C) 20%
D) 400%
E) 25%

Question 44

Which of these energy transformations best describes the overall operation of a hydroelectric power plant?

A) grav E ·therm E
B) electromag E ·grav E
C) thermal E ·electromag E
D) grav E ·electromag E
E) chem E ·electromag E

Question 45

Regarding the validity of the law of conservation of energy,

A) this law is a consequence of Newtonian physics, and so this law is valid in every known situation because Newtonian physics is valid in every known situation.
B) it is valid for any situation in which Newtonian physics is valid, but is often incorrect outside of that range.
C) it is valid in all situations except those situations involving heat.
D) it is valid in every known situation-- including those situations in which Newtonian physics is not valid.

Question 46

You throw a baseball horizontally, and Jill catches it. Neglect air resistance. The energy transformation that occurs during the throw [while the ball is in your hand] is

A) chemical E ·kinetic E.
B) chemical E ·gravitational E.
C) kinetic E ·thermal E.
D) thermal E ·kinetic E.
E) kinetic E ·chemical E.

Question 47

A gas can containing a gallon of gasoline is stored in a basement. This gasoline contains

A) energy.
B) both work and energy.
C) both energy and power.
D) work.
E) neither work nor energy.

Question 48

The power of American automobiles is usually rated in "horsepower." What other units could be used?

A) watts
B) joules
C) Calories
D) None of the above.
E) All of the above.

Question 49

What form or forms of energy does a falling elastic ball have when it is at its most- squeezed position on the floor, before it begins to rebound [see figure above]?

A) Kinetic and gravitational and elastic
B) Gravitational only
C) Elastic only
D) Kinetic and elastic
E) Kinetic only

Question 50

A block of ice slides freely [no air resistance, no friction] down a slippery slope. The block starts from rest at the top of the slope, where it has a vertical height of 4 m above the bottom of the slope and where it has a gravitational energy of 1000 J. At a quarter of the way down the slope, the block's gravitational energy is

A) 250 J.
B) 500 J.
C) 750 J.
D) 1000 J.
E) less than 250 J.

Question 51

Suppose you slowly, and at constant speed, lift a book weighing 12 N from the floor to a shelf 2 m above the floor. Neglect air resistance. The work done by you on the book is

A) zero.
B) 6 joules.
C) 24 watts.
D) 6 watts.
E) 24 joules.

Question 52

In order to quadruple an object's kinetic energy, we must

A) stretch it twice as far.
B) quadruple its height.
C) double its height
D) double its speed.
E) quadruple its speed.

Question 53

There are no known exceptions to

A) the law of conservation of energy.
B) Newton's law of motion.
C) Both of the above.
D) Nonsense-- all physical principles have known exceptions.

Question 54

One situation in which the law of conservation of energy is violated is

A) for very fast- moving objects.
B) for atomic- sized objects.
C) near black holes.
D) All of the above.
E) nonsense-- no violations of this law have ever been observed.

Question 55

Under what condition can a force act on an object and yet do no work on that object?

A) If the object moves with no acceleration.
B) If the net force on the object is zero.
C) If the object does not move.
D) If the force operates at constant (unchanging) power.
E) Nonsense-- any force on an object must do work on that object.

Question 56

Elizabeth lifts a 10 N book from the floor to the table, a height of 2 m. How much work does Elizabeth do?

A) 5 joules
B) 5 watts
C) 20 watts
D) 20 joules
E) Elizabeth does zero work

Question 57

Which of the following energy transformations represents the operation of a wind turbine [a device that uses the wind as an energy resource]?

A) Thermal E ·Electric E
B) Kin E ·Electric E
C) Grav E ·Electric E
D) Electric E ·Kin E

Question 58

A block of ice slides freely [no air resistance, no friction] down a slippery slope. The block starts from rest at the top of the slope, where it has a vertical height of 4 m above the bottom of the slope and where it has a gravitational energy of 1000 J. The block's total energy a quarter of the way down the slope [at a height of 3 m] is

A) 250 J.
B) 500 J.
C) 750 J.
D) 1000 J.
E) greater than 1000 J.

Question 59

A physics professor pushes against a stationary wall, "working" up a sweat. Is he doing any actual physical work on the wall?

A) No-- it's a law of nature that physics profs never do any actual work.
B) No, because the wall is not moving.
C) Yes, because his arm muscles are moving other muscles through a distance.
D) Yes, because he is exerting a force against the wall during a period of time.
E) No, because the force by his hands against the wall is balanced by the force by the wall pushing back.

Question 60

You push your physics book across your desk, leaving the book at rest on the desk at the end of the process. Which of the following best represents the overall energy conversion during this process?

A) elastic to thermal
B) thermal to chemical
C) chemical to thermal
D) chemical to electromagnetic
E) kinetic to thermal

Question 61

The "energy efficiency" of a device is

A) the total energy put into the device divided by its useful energy output.
B) its useful energy output divided by the total energy put into the device.
C) its total energy output divided by the total energy put into the device.
D) its thermal energy output divided by the total energy put into the device.
E) the total energy put into the device divided by its thermal energy output.

Question 62

A 100 W lightbulb has an energy efficiency of 5%. It is turned on for one minute. Its total energy output during this minute is

A) 5700 J.
B) 300 J.
C) 6000 J.
D) impossible to determine because we don't know the voltage.
E) impossible to determine because we don't know the power.

Question 63

Which one of our 8 standard physical forms of energy is present in gasoline?

A) thermal
B) chemical
C) kinetic
D) radiant
E) solar

Question 64

In order for you to get out of bed with the least amount of work, would it be better for your bed to be on the floor or a meter high?

A) It makes no difference, because you must change your position from lying down to standing up in either case.
B) It makes no difference, because the total amount of physical work done in either case is zero.
C) Both of the above.
D) It would be better for the bed to be a meter high, because then you would not need to do as much work in lifting yourself to your feet.
E) It would be better for the bed to be on the floor, because then you would not need to do as much work to get your feet down onto the floor.

Question 65

At 10 cents per kilowatt- hour, how much does it cost to run a 100 watt lightbulb for 200 hours every month?

A) 20 cents per month
B) $2 per month
C) $20 per month
D) impossible to determine because we don't know the voltage
E) impossible to determine because we don't know the power

Question 66

Physically, the type of energy represented by the water behind a dam is

A) chemical.
B) kinetic.
C) electromagnetic.
D) thermal.
E) gravitational.

Question 67

The sub- atomic particle known as the "neutrino" was originally hypothesized

A) in order to preserve the law of conservation of energy in a certain type of nuclear process.
B) because it was thought that thermal energy (or heat) is actually a form of energy.
C) in order to preserve Newton's laws in a certain type of nuclear process.
D) in order to preserve conservation of electric charge in a certain type of nuclear process.
E) because it was thought that radiant energy is actually a form of energy.

Question 68

Thermal energy can be described as

A) macroscopic kinetic energy.
B) microscopic kinetic energy.
C) Both of the above.
D) None of the above.

Question 69

A 2000 N car travels 50 m along a level road, powered by a drive force of 1000 N. The work done by the drive force is

A) 1000 J.
B) 2000 J.
C) 50,000 J.
D) 10,000 J.
E) zero.

Question 70

James Prescott Joule's experiments, such as stirring a container full of liquid, showed that

A) Mr. Joule did not know how to make a good batch of chili.
B) thermal energy is actually a form of energy.
C) all forms of energy are conserved.
D) the "Newtonian" energy forms [kinetic, gravitational, elastic] are conserved.
E) radiant energy is actually a form of energy.

Question 71

You lift a book slowly from the floor to the table. You then lift an identical book rapidly from the floor to the table. Compared with the slow process, in the faster process your

A) energy output [i.e., amount of energy transformed into gravitational energy] is greater.
B) work done is greater.
C) Both of the above are correct.
D) power output is greater.
E) All of the above are correct.

Question 72

"Energy" could best be defined as

A) matter in motion.
B) the amount of force a system is capable of exerting.
C) the ability to exert power.
D) stored momentum.
E) the capacity to do work.

Question 73

Are the laws of energy [conservation of energy, and 2nd law of thermodynamics] known for certain to be true?

A) No; in fact these laws are known to be violated at sufficiently high speeds, small distances, and large distance.
B) No, because all scientific laws are tentative.
C) No, for both of the above reasons.
D) Yes, because despite repeated checking they have never been found to be false.
E) Yes because, unlike some of the other laws, these laws are true by logical deduction from a priori premises.

Question 74

A certain meteoroid [a rock in space] has been moving through our solar system ever since the solar system was formed, 5 billion years ago. Suppose the meteoroid is far from all planets and stars, so that the effect of gravity is negligible. Neglecting gravity, is any physical work being done on the meteoroid?

A) Yes, because the force of inertia is exerted on the meteoroid while the meteoroid moves.
B) No, because the force of inertia on the meteoroid is balanced by the equal reaction force by the meteroid.
C) Yes, because the meteoroid is moving.
D) Yes, because work is always required to move any massive object through a distance.
E) No, because no forces are exerted on the meteoroid.

Question 75

When water evaporates from the ocean and rises into the atmosphere, the energy transformation is

A) gravitational energy ·electromagnetic energy.
B) kinetic energy ·thermal energy.
C) chemical energy ·gravitational energy.
D) chemical energy ·thermal energy.
E) radiant energy ·gravitational energy.

Question 76

You throw a baseball horizontally, and Jill catches it. Neglect air resistance. The energy transformation that occurs during the catch is

A) thermal E ·kinetic E.
B) chemical E ·gravitational E.
C) kinetic E ·thermal E.
D) kinetic E ·chemical E.
E) chemical E ·kinetic E.

Question 77

What energy transformation occurs during photosynthesis?

A) chemical E ·kinetic E
B) radiant E ·kinetic E
C) thermal E ·chemical E
D) chemical E ·thermal E
E) radiant E ·chemical E

Question 78

You run a 5000 watt clothes- dryer for 2 hours. How many kilowatt- hours of energy did you consume?

A) 0.4
B) 10
C) 2.5
D) 2500
E) Cannot be determined from the given information

Question 79

One car is traveling twice as fast as a second car. How much more work can the first car do. compared to the second car, in smashing into a brick wall?

A) three times as much
B) the same amount as the second car
C) twice as much
D) four times as much
E) All of the above.

Question 80

What form(s) of energy does the falling rubber ball have when it is halfway down (see figure)?

A) Gravitational only
B) Kinetic and gravitational and elastic
C) Kinetic only
D) Elastic only
E) Kinetic and gravitational