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Physics > Energy > Flashcards

Energy Flashcards

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1
Q

Kinetic energy

A

Stored in moving objects

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2
Q

Equation for kinetic energy

A

0.5 x mass (kg) x velocity² (m/s)

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3
Q

How do things move?

A

Chemical energy store in the thing ——> kinetic energy in movement

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4
Q

Gravitational potential energy

A

Stored in an object due to position above earth’s surface

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5
Q

Gravitational potential energy equation

A

Mass (kg) x gravitational field strength (N/kg) x height (m)

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6
Q

Elastic potential energy

A

Stored in stretched/ compressed objects
By putting energy into it by squeezing/ stretching it will store it as elastic potential energy

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7
Q

Elastic potential energy equation

A

0.5 x spring constant (N/kg) x extension² (m)

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8
Q

What is the spring constant of an object?

A

A measure of the ratio a force is applied to it and the extension caused by it

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9
Q

Extension in elastic objects

A

The extra bit in a spring caused when stretching it

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10
Q

Can extension in a spring be negative?

A

Yes if compressed

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11
Q

Internal energy

A

Total kinetic and potential energy in particles
Usually vibrations of solid particles

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12
Q

What happens if you increase the force applied on a spring?

A

It will extend
Directly proportional to the force applied

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13
Q

Hooke’s law

A

Force and extension are directly proportional
By being multiplied by a spring constant

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14
Q

Limit of proportionality

A

When a spring has been stretched beyond its limit
So when the force is removed it no longer returns back to its original position = no longer directly proportional

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15
Q

Energy transfer

A

When energy is transferred from one store to another
Also known as work being done

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16
Q

Law of conservation of energy

A

Energy can be transferred to another store, stored, or dissipated
but NEVER made or destroyed

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17
Q

System

A

An object/ group of objects

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18
Q

Closed system

A

When no energy can enter or leave so the total amount stays constant
Even after transfers

19
Q

Energy transfers in a pendulum

A

At the furthest point on the side it has highest gpe
Swings down and transfers to kinetic energy
Repeats then eventually stops due to air resistance

20
Q

Energy transfers in bungee jumper

A

Gpe store at highest point
Jumps, begins transferring to Ek
Maximum Ek
Rope tightens and all Ek ——> Ee due to extension caused by force. Stops moving
Rope recoils, Ee——> Ek
Moving upwards = back to Gpe

21
Q

What is a result of friction on energy transfer?

A

Friction causes some energy transferred to thermal energy
So surrounding temperature increases
If this repeats the system may stop moving due to all transferred to thermal energy

22
Q

How to stop unwanted energy transfer ?

A

Use lubricant = less rubbing and friction
Remove air particles around

23
Q

Types of energy transfer

A

Mechanical (using force to move)
Electrical (voltage)
Heating
Radiation

24
Q

Work done equation

A

Work done (J) = Force (N) x distance (m)

25
Q

What can work be measured in?

A

J or N/m

26
Q

Power

A

The rate at which energy is transferred/ work is done

27
Q

High power object

A

Transfers energy fast

28
Q

Low power

A

Transfers energy slow

29
Q

What is power measured in?

A

Watt (W)

30
Q

Power equation

A

Energy —-> /work done (J)
———————————————
Time (s)

31
Q

Efficiency

A

The percent of energy we put in is transferred to useful store
Because some is transferred to unwanted stores

32
Q

What can we use to calculate efficiency

A

Power
or
Energy transfer

33
Q

Using power to calculate efficiency

A

Useful power output
——————————
Total power input
(x100)

34
Q

Using energy transferred to calculate efficiency

A

Useful output energy transfer
——————————————
Total input energy transfer
(x100)

35
Q

How to increase efficiency when heating water?

A

Use a lid = stop heat transfer up
Use insulating material to prevent transfer from sides
Put heat source inside the appliance like a kettle
Use large base so all energy transfer into the pan

36
Q

Thermal conductivity

A

The rate of thermal energy transfer by conduction across a material

37
Q

High thermal conductivity

A

Higher rate of energy transfer so object will cool faster
If trying to preserve energy = BAD

38
Q

Low thermal conductivity

A

Slow rate of energy transfer so object stays warm faster
If trying to keep heat in = GOOD

39
Q

Where can heat transfer through in a house?

A

Walls
Windows
Loft

40
Q

How to insulate a wall

A

There’s usually a cavity heat can transfer through easily between exterior and interior wall
So use insulating material between = low thermal conductivity

41
Q

How to insulate a window

A

Double glazed for low thermal conductivity

42
Q

How to insulate a loft

A

Use loft insulation

43
Q

Why do we want to decrease the heat transfer in homes?

A

So we can reduce energy costs

Physics (44 decks)

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