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physics > chapter 10 > Flashcards

chapter 10 Flashcards

1
Q

forms of energy

A

dolphin: kinetic energy as it leaves the water. At its highest point its energy is mostly potential energy.

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2
Q

work on the jack,

A

applying a force to the handle and pushing it down. This is a transfer of energy into the system, increasing the potential energy as the car is lifted.

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3
Q

slide

A

As they slide, their potential energy decreases and their kinetic energy increases, but their total energy is unchanged

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4
Q

total energy

A

E

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5
Q

A weightlifter lifts a barbell over her head

A

The barbell has much more gravitational potential energy when high above her head than when on the floor. To lift the barbell, she transforms chemical energy in her body into gravitational potential energy of the barbell.

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6
Q

A base runner slides into the base

A

When running, he has lots of kinetic energy. After sliding, he has none. His kinetic energy is transformed mainly into thermal energy: The ground and his legs are slightly warmer.

K → Eth

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7
Q

A burning campfire

A

The wood contains considerable chemical energy. When the carbon in the wood combines chemically with oxygen in the air, this chemical energy is transformed largely into thermal energy of the hot gases and embers.

Echem → Eth

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8
Q

A springboard diver

A

Here’s a two-step energy transformation. At the instant shown, the board is flexed to its maximum extent, so that elastic potential energy is stored in the board. Soon this energy will begin to be transformed into kinetic energy; then, as the diver rises into the air and slows, this kinetic energy will be transformed into gravitational potential energy.

Us→ K → Ug

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9
Q

In order for energy to be transferred as work, the system must undergo a displacement—it must move—during the time that the force is applied.

A

Thus work is done on a system by forces outside the system; we call such forces external forces.

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10
Q

Internal forces—forces between objects within the system—cause energy transformations within the system but don’t change the system’s total energy. In order for energy to be transferred as work, the system must undergo a displacement—it must move—during the time that the force is applied.

A

-

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11
Q

the larger the displacement, the greater the work done

A

-

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12
Q

The stronger the force, the greater the work done.

A

-

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13
Q

w=fd

A

work equation

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14
Q

joule

A

1 j= 1nm

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15
Q

the joule is the unit of all forms of energy

A

-

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16
Q

work, unlike momentum, is a scalar

A

scalar

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17
Q

work

A

force d cos theta

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18
Q

Example 10.2 Work done in pulling a suitcase

A

It’s 120 m from one gate to another in the airport. You use a strap inclined upward at a 45° angle to pull your suitcase through the airport. The tension in the strap is 20 N. How much work do you do?- in book

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19
Q

translational kinetic energy

A

We’ll start with the case of an object in motion along a line.

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20
Q

blade of a wind turbine, rotating about a fixed axis

A

rotational kinetic energy

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21
Q

translational kinetic energy formula

A

F→ while the car undergoes a displacement d→, so the force does work W=Fd on the car. If we ignore friction and drag, the work done by F→ is transferred entirely into the car’s energy of motion—its kinetic energy. In this case, the change in the car’s kinetic energy is given by the work-energy equation, Equation 10.3, as

W=ΔK=Kf−Ki

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22
Q

Gravitational potential energy depends only on the height of an object and not on the path the object took to get to that position.

A

elastic (or spring) potential energy Us. We can find out how much energy is stored in a spring by using an external force to slowly compress the spring. This external force does work on the spring, transferring energy to the spring. Since only the elastic potential energy of the spring is changing, Equation 10.3 becomes
ΔUs=W

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23
Q

thermal energy Eth

A

sum of all these microscopic potential and kinetic energies is what we call

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24
Q

kinetic energy

A

k=1/2 mv

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25
Q

work

A

force (displacement)

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26
Q

Energy

A

central concept in physics

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27
Q

Energy

A

K+u+constant

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28
Q

A collision in which mechanical energy is conserved is called a

A

perfectly elastic collision

29
Q

1 watt

A

1 joule/second

30
Q

1 horsepower

A

746 W

31
Q

P=

A

fv

32
Q

specific power

A

power of a transformation or a transfermass of agent causing the transformation or transfer

33
Q

elastic potential energy

A

Us =1/2 kx2

34
Q

elastic potential energy

A

elastic to kinetic then gravitational energy

35
Q

law of conservation of energy

A

Energy is neither created nor destroyed: If one form of energy in a system decreases, it must appear in an equal amount in another form. Many scientists consider this law of conservation of energy to be the most important of all the laws of nature.

36
Q

total energy

A

every system in nature has associated with it a quantity we call

37
Q

joule

A

unit of form of all types of energy

38
Q

kinetic energy

A

an object’s energy of motion

39
Q

Work

A

force(distance)

40
Q

gravitational potential energy

A

up at the top

41
Q

total energy

A

every system in nature has associated with it a quantity we call its

42
Q

energy of one kind can be transformed into another

A

If the amounts of each form of energy never changed, the world would be a very dull place. What makes the world interesting is that energy of one kind can be transformed into energy of another kind

43
Q

A weightlifter lifts a barbell over her head

A

Echem → Ug

44
Q

A base runner slides into the base

A

Echem → eth

45
Q

A burning campfire

A

The wood contains considerable chemical energy. When the carbon in the wood combines chemically with oxygen in the air, this chemical energy is transformed largely into thermal energy of the hot gases and embers.

Echem → Eth

46
Q

A springboard diver

A

Us→ K → Ug

47
Q

An exchange of energy between system and environment is called an energy transfer

A

work, the mechanical transfer of energy to or from a system by pushing or pulling on it, and heat, the nonmechanical transfer of energy from the environment to the system (or vice versa) because of a temperature difference between the two.

48
Q

ΔE=W

A

change in the system’s energy as ΔE

49
Q

The work-energy equation

The total energy of a system changes by the amount of work done on it:

A

ΔE=ΔK+ΔUg + ΔUs + ΔEth + ΔEchem+⋯=W(10.3)

50
Q

isolated system,

A

the total energy of an isolated system is conserved.

51
Q

Law of Conservation of Energy

The total energy of an isolated system remains constant:

A

ΔE=  ΔK+ ΔUg+ ΔUs+ ΔEth+  ΔEchem+ ⋯ = 0

52
Q

the larger the displacement, the greater the work done. Second, if the wind pushes with a stronger force, the surfer speeds up more rapidly, and the change in his kinetic energy is greater than with a weaker force. The stronger the force, the greater the work done.

A

….

53
Q

W=FdWork done by a constant force F→ in the direction of a displacement d→

A

……

54
Q

1 joule=1 J=1 N⋅m

A

the joule is the unit of all forms of energy.

55
Q

work, unlike momentum, is a scalar quantity

A

……

56
Q

W=F||d=Fd cos θWork done by a constant force F→ at an angle θ to the displacement d→

A
57
Q

The quantities F and d are always positive, so the sign of W is determined entirely by the angle θ between the force and the displacement.

A

–

58
Q

negative work represents a transfer of energy out of the system.

A

–

59
Q

The energies present in an isolated system can transform from one kind into another, but the total energy is conserved. The unit of all types of energy is the joule (J).

A

k=1/2mv^2

60
Q

The breaking of molecular bonds by the absorption of light is called

A

photodissociation.

61
Q

10.4 Potential energy

A

since it has the potential to be converted into other forms of energy, such as kinetic or thermal energy.

62
Q

gravitational potential energy Ug, let’s consider the system of the book and the earth shown in Figure 10.13a. The book is lifted at a constant speed from its initial position at yi to a final height yf

A
63
Q

ΔUg=W

A

work-energy equation

64
Q

Ug=mgy

A

Gravitational potential energy of an object of mass m at height y(assuming Ug=0 when the object is at y=0)

65
Q

This means that each atom has on average a higher potential energy.

A
66
Q

thermal energy Eth

A

sum of all these microscopic potential and kinetic energies

67
Q

ΔEth=fkΔx

A
68
Q

If an object moves through air, water, or another fluid at a constant speed, there is a constant drag force opposite the motion, so we can do an analysis similar to that for the friction force. If we consider the object + fluid to be the system, as the object moves at a constant speed, the drag force D transforms energy into thermal energy

A

ΔEth=DΔx

69
Q

work-energy equation can be written as

A

ΔK+ΔU+ΔEth=W

physics (10 decks)

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