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Phys > Chapter 1- Energy > Flashcards

Chapter 1- Energy Flashcards

1
Q

GPE equation

A

Ep=mgh

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2
Q

Kinetic Energy equation

A

E = 0.5x m x v²

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3
Q

Work Done equation

A

Work=FS

s=distance

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4
Q

what is efficiency

A

efficiency tells us how good a transformer is at doing its job

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5
Q

efficiency equation

A

Efficiency = useful energy ÷ total energy

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6
Q

does efficiency have units?

A

no

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7
Q

power equation

A

power(watts(w))=energy(J)/time(s)

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8
Q

calculating efficiency from power

A

Efficiency=useful power output/total power input

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9
Q

what is a Mw

A

mega watt- 1 million watts

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10
Q

what is a kw

A

a kilowatt-1 thousand watts

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11
Q

what is thermal energy?

A

A type of energy that will flow from a warm area to a cold areas until it reaches the temperature of the surrounding(until it is all equal)

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12
Q

list the three ways energy can move

A

conduction, convection or radiation

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13
Q

what is a similarity between convection and conduction?

A

both involve particles gaining kinetic energy

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14
Q

what is infrared radiation?

A

electromagnetic waves between visible light and microwaves

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15
Q

Momentum equation ( involving mass and velocity)

A

Momentum = mass X velocity

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16
Q

Why doesn’t a bungee jumper bounce back to the top?

A

Because the gravitational field strength is pulling you down stoppiy you from going to your original height

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17
Q

what is work done

A

when a force moves an object through a distance

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18
Q

what is mechanical work

A

energy transferred from one object to another by force

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19
Q

what is waves (energy transforming/transfers)

A

Light + other types of energy transferred from one energy store to another

20
Q

Heating (energy transforms/ transfers)

A

Heating an object transfers energy from the object’s internal store of energy

21
Q

how does conduction transfer energy?

A

conduction passes energy from one particle to another (by vibrating) the partices do not move

22
Q

why are metals good thermal conductors?

A

They have free electrons to carry energy

23
Q

what is specific heat capacity?

A

the amount of energy required to raise 1kg of material by 1℃

24
Q

specific heat capacity equation

A

Energy=mass(kg)x specific heat capacity(J/Kg℃)x temperature change(℃)

25
Q

Why are metals good thermal conductors and non metals not so good

A

metals are good thermal conductors
because they have free electrons to
carry energy. non metal solids are
usualy poor conductors because they
need atomic vibrations to carry energy

26
Q

advantages of wind and solar power

A

•Low running costs
•Don’t release pollutants
•Don’t damage the environment
•Getting cheaper every year

27
Q

Disadvantages of wind and solar power

A

•High upfront cost
•Making them does produce pollutants
•Dependent on the weather
0149No way to inc supply in a time of demand

28
Q

Advantages and disadvantages of hydroelectricity and tidal barrages

A

Advantages:
•Renewable
•large amounts of energy transferred
•no pollutants
•Reliable
•Hydroelectricity- immediate response to increased demand
•Running costs fairly low
•Work on both large and small scales

Disadvantages:
•Often flood
•Often big impact on environment (flood habitat, noise pollution, installation destroys some habitats
•Stops boats+ fish swimming up stream
Initail set up is expensive

29
Q

what is specific heat capacity?

A

the amount of energy required to raise the temperature of 1kg of material by 1 degrees Celsius

29
Q

what is specific heat capacity?

A

the amount of energy required to raise the temperature of 1kg of material by 1 degrees Celsius

30
Q

what units is g measured in?

A

N/kg

31
Q

When an object falls describe the energy changes

A

When an object falls the GPE store is converted into the kinetic energy store

Without resistance energy lost from gpe=energy gained in Ek store

(However in real life some energy is transferred to other energy stores e.g thermal energy of the object and its surroundings

32
Q

What is the power of an appliance defined as ?

A

The Power of the appliance (in watts)-is the energy
it transforms in Joules per second(J/s) Aka watts (W)

33
Q

Why are metals good conductors of thermal energy

A

Because they have free electrons to carry energy

34
Q

How does thermal energy behave

A

Thermal energy will flow from a warm area to a colder area until the temperature of the surroundings are even(almost like diffusion)

35
Q

Why are non-metals not good at conducting thermal energy

A

Because they need atomic vibrations to carry energy

36
Q

What is conduction?

A

Conduction is the process where vibrating particles transfer energy to neighbouring particles

37
Q

How does the energy transfer in conduction which energy transfers?

A

Energy transferred by heating is transferred
to the thermal energy store of the object. this
energy is shared across the kinetic energy stones
of the particles in the object.

38
Q

What does a hot object emit

A

Infrared radiation

39
Q

White surfaces in terms of infrared radiation (are they good absorbers/ emitters, are they good or bad reflectors)

A

White surfaces are good reflectors of it radiation
But poor emitters and absorbers of ir radiation

40
Q

Shiny Surfaces in terms of infrared radiation (are they good absorbers/ emitters, are they good or bad reflectors)

A

Poorer absorbers of radiation than dull surfaces of the same colour
Poorer emitters and better reflectors than dull surfaces of the same colour

41
Q

Black surfaces in terms of infrared radiation (are they good absorbers/ emitters, are they good or bad reflectors)

A

Good emitters
Good absorbers
Poor reflectors

Of radiation

42
Q

Space blankets are designed to keep runners warm after marathons. They are shiny on both sides. Suggest why the shiny sides may help keep runners warm

A

The runner is hotter than their surroundings, so heat needs to be trapped inside the blanket. The inner surface of the blankets is shiny to reflect any infra-red radiation from the runner’s body back to the runner.
Any heat that is transferred to the blanket would then be emitted as infra-red to the outside world, so the outer side is shiny to reduce the infra-red emission to the surroundings.

43
Q

List two ways to reduce friction

A

Using Lubricants
Using smoother surfaces

44
Q

how does Surface Area affect emission of radiation

A

Bodies with a large surface area will emit radiation faster.

Phys (13 decks)

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