Chapter 7: Energy (From Lecture Slide) Flashcards

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1
Q

Energy

A

A property that can be used to determine how an object can change its state of motion or its physical shape

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2
Q

Energy existed in

A

Potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms

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3
Q

All forms of energy are associated with

A

Motion

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4
Q

Principle conservation of energy

A

Energy can be neither created nor destroyed but only changed from one form to another

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5
Q

Energy is the property of a system that enables it to do

A

Work

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6
Q

Energy observed when it is

A

Being transferred or being transformed

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7
Q

Energy any given body has kinetic energy if it is in

A

Motion

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8
Q

A bow or spring has the potential for creating

A

Motion; it contains potential energy

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9
Q

Nuclear energy is

A

Potential energy becuase it results from the configuration of subatomic particles in the nucleus of an atom

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10
Q

Energy (Definition) is the

A

Property of a system that can be used to do work or to heat

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11
Q

Energy can be transferred but

A

Total amount in the universe does not change

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12
Q

Work

A

How long the force acts over a distance

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12
Q

Matter is

A

Substance we can see, smell, and feel and has mass and occupies space

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13
Q

Impulse

A

How long the force acts over time interval

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14
Q

A transfer of energy over a distance by

A

Some applied external force

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14
Q

Work are include three mains part of the conceptually

A

1) Involves force and distance
2) Is force times distance
3) In equation form: W = Fd

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15
Q

Two things occur whenever work is done:

A

1) A force acts on an object
2) The object subject to the force

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16
Q

If you push against a stationary brick wall for several minutes, you do not work

A

You may do work on your muscles, which stretch and contract, but not on the wall because the wall does not move

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16
Q

Twice as much work is

A

Done in lifting two loads 1 story high versus lifting 1 load the same vertical distance

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16
Q

Why twice as much work is?

A

Force needed to lift twice, the load is twice as much

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16
Q

Is there work being done in lifiting the barbell?

A

There is a force required to lift the weight of the barbell off the ground to a distance above the weightlifter’s head.

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16
Q

Work is done in lifiting a barbell. How much work is done in lifting a barbell that is twice as heavy the same distance?

A

This is in accord with work equals to the force x distance. Twice the force for the same distance means twice the work done on the barbell

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16
Q

You do work when pushing a cart with a constant force. If you push the cart twice as far, then the work you do is

A

Twice as much

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17
Q

A job can be done slowly or quickly. These methods require the same amount of work, but different amounts of

A

Power is the rate of which work is done, so doing the job faster requires more power

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18
Q

Mechanical energy is

A

In each something has been acquired that these object to do enables work

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19
Q

Mechanical energy is

A

Due to position or to or both these motions

20
Q

There are two form of mechanical energy are

A

1) Potential
2) Kinetic

21
Q

Potential energy: an object has by means of position

A

Stored energy held in readiness with a potential

22
Q

Gravitaitional potential energy

A

Work is required to elevated objects against Earth’s gravity

23
Q

The potential energy due to

A

Elevated

23
Q

Whenever work is done to

A

Lift and energy is exchanged

24
Q

The amount of gravitational potential energy possessed by an elevated object is

A

Equal to the work done against gravity in lifting it

25
Q

The height is the distance above some chosen

A

A reference level such as the ground or the floor of a building.

26
Q

Does a crate lifted by a pulley have increased potential energy relative to the floor?

A

If the crate were twice as heavy, its increase in potential energy would be twice as great

27
Q

Does a car hoisted for repairs in a service station have increased potential energy relative to the floor?

A

Yes, if the car were twice as heavy, its increase in potential energy would be twice as great

28
Q

What happen if the ball rolls down the end of the ramp?

A

Potential energy changes into kinetic energy

29
Q

If an object is moving, it is capable of doing work

A

Depends on mass and speed

30
Q

If an object’s speed is doubled, its kinetic energy is

A

Quadruptle

31
Q

Does a car with momentum have kinetic energy?

A

Yes, because the car is in motion - Anything in motion necessarily has kinetic energy, regardless of whether it is accelerating or not

32
Q

Net work is based on

A

The net force applied to the object and net force is combined with applied force and friction force

33
Q

The net work equals the change in

A

Kinetic energy

34
Q

Any change in kinetic energy is the restoring

A

Thermal energy

35
Q

Only part of the total work that you do changes the object’s

A

Kinetic energy

36
Q

The rest is changed by friction into

A

Thermal energy

37
Q

How does energy transform?

A

Energy can change one form to another, and one location to another: heat and electromagnetic

38
Q

Law of Conservation of Energy

A

Energy cannot be created or destroyed, it may be transformed from one form into another, but the total amount of work

39
Q

Comparing kinetic energy and momentum (similarities)

A

Similarities between momentum and kinetic energy are both are properties of moving things

40
Q

Comparing kinetic energy and momentum (differences)

A

1) Momentum is a vector quantity and therefore is directional and can be canceled
2) Kinetic energy is a scalar quantity and can never be canceled

41
Q

An object moving with twice the velocity of another with the same mass, has

A

Twice the momentum but four times the kinetic energy

42
Q

Machine device for

A

Multiplying forces or changing the direction of forces

43
Q

Principle of underlying of every machine is

A

Conservation of energy

44
Q

Machine cannot create energy but can transform energy

A

From one form to another or transfer energy from one location to another

45
Q

Example of simple machines are

A

1) Lever
2) Pulley

46
Q

Lever rotates on a point of support called

A

The fulcrum

47
Q

Lever arms allows a small force over a large distance to

A

Induce a large force over a short distance

48
Q

We do work on one end of the lever and the other end

A

Does work on the load

49
Q

Fulcrum and point of support

A

It is closer to load (weight), small force over larger distance equal to larger force over a smaller distance

50
Q

Pulley operates like a lever with

A

Equal arms, changes the direction of the input force

51
Q

Lever and pullies are

A

Ideal system and operate at 100% efficiency (100% of work input = 100% of work ouput)

52
Q

Energy is lost (dissipiated) through

A

Molecular kinetic energy and thermal energy

53
Q

The lower the effficiency of a machine,

A

The greater the percentage of energy is lost to thermal energy

54
Q

Efficiency

A

Percentage of work put into a machine that is converted into useful work output

55
Q

Source of Energy: Concentrated energy

A

1) Nuclear Power
2) Stored in uranium and plutonium
3) By product is geothermal energy
4) Held in underground reservoirs of hot water to provide steam that can drive turbogenerators