Energy

Question 1

Kinetic energy

Answer 1

Stored in moving objects

Question 2

Equation for kinetic energy

Answer 2

0.5 x mass (kg) x velocity² (m/s)

Question 3

How do things move?

Answer 3

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

Question 4

Gravitational potential energy

Answer 4

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

Question 5

Gravitational potential energy equation

Answer 5

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

Question 6

Elastic potential energy

Answer 6

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

Question 7

Elastic potential energy equation

Answer 7

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

Question 8

What is the spring constant of an object?

Answer 8

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

Question 9

Extension in elastic objects

Answer 9

The extra bit in a spring caused when stretching it

Question 10

Can extension in a spring be negative?

Answer 10

Yes if compressed

Question 11

Internal energy

Answer 11

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

Question 12

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

Answer 12

It will extend
Directly proportional to the force applied

Question 13

Hooke’s law

Answer 13

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

Question 14

Limit of proportionality

Answer 14

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

Question 15

Energy transfer

Answer 15

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

Question 16

Law of conservation of energy

Answer 16

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

Question 17

System

Answer 17

An object/ group of objects

Question 18

Closed system

Answer 18

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

Question 19

Energy transfers in a pendulum

Answer 19

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

Question 20

Energy transfers in bungee jumper

Answer 20

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

Question 21

What is a result of friction on energy transfer?

Answer 21

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

Question 22

How to stop unwanted energy transfer ?

Answer 22

Use lubricant = less rubbing and friction
Remove air particles around

Question 23

Types of energy transfer

Answer 23

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

Question 24

Work done equation

Answer 24

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

Question 25

What can work be measured in?

Answer 25

J or N/m

Question 26

Power

Answer 26

The rate at which energy is transferred/ work is done

Question 27

High power object

Answer 27

Transfers energy fast

Question 28

Low power

Answer 28

Transfers energy slow

Question 29

What is power measured in?

Answer 29

Watt (W)

Question 30

Power equation

Answer 30

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

Question 31

Efficiency

Answer 31

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

Question 32

What can we use to calculate efficiency

Answer 32

Power or Energy transfer

Question 33

Using power to calculate efficiency

Answer 33

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

Question 34

Using energy transferred to calculate efficiency

Answer 34

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

Question 35

How to increase efficiency when heating water?

Answer 35

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

Question 36

Thermal conductivity

Answer 36

The rate of thermal energy transfer by conduction across a material

Question 37

High thermal conductivity

Answer 37

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

Question 38

Low thermal conductivity

Answer 38

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

Question 39

Where can heat transfer through in a house?

Answer 39

Walls Windows Loft

Question 40

How to insulate a wall

Answer 40

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

Question 41

How to insulate a window

Answer 41

Double glazed for low thermal conductivity

Question 42

How to insulate a loft

Answer 42

Use loft insulation

Question 43

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

Answer 43

So we can reduce energy costs