energy

Question 1

what is the equation for kinetic energy?

Answer 1

1/2 x mass x velocity (squared)

Question 2

what is the equation for elastic potential energy?

Answer 2

1/2 x spring constant x extension (squared)

Question 3

what is the equation for gravity potential energy?

Answer 3

mass x gravitational field strength x height

Question 4

define specific heat capacity of a substance

Answer 4

the amount of energy needed to raise the temperature of 1 kilogram of a substance by 1 degree celsius.

Question 5

state the units for specific heat capacity

Answer 5

joules
degree celsius
kilogram

Question 6

what is the definition of power

Answer 6

the rate at which energy is transferred
or
rate at which work is done

Question 7

state the two equations for power

Answer 7

power = energy transferred / time
power = work done / time

Question 8

what is the unit of power

Answer 8

watt

Question 9

two motors lift the same mass through the same height.
motor A does this in half the time of motor B
which dissipates the most power

Answer 9

motor a
the energy is transferred is the same but the time taken is less

Question 10

describe the energy changes involved when a ball is thrown upwards and then returns to tis starting position.

Answer 10

upwards: KE is converted to GPE
peak: maximum GPE, zero KE
downwards: GPE is converted to KE

Question 11

describe the energy transfers for a bungee jumper

Answer 11

• when falling, the GPE is converted to KE of jumper
• as cord tightens, KE is converted and stored as elastic potential energy
• at lowest point, the jumpers initial GPE equals the EPE stored in the cord

Question 12

explain why a bungee jumper slows down once the cord begins to stretch

Answer 12

• kinetic energy decreases since it is converted to elastic potential energy
• since KE is proportional to velocity (squared), as KE decreases so does velocity

Question 13

examples of chemical energy stores

Answer 13

• food
• fuel
• batteries

Question 14

state 4 different stores of energy

Answer 14

1. kinetic energy
2. gravitational potential energy
3. elastic potential energy
4. chemical changes

Question 15

state the law of energy conservation

Answer 15

energy cannot be created or destroyed (it can only be transferred into different forms)

Question 16

state the changes in the total energy of a ball that is kicked, assuming that no external forces act

Answer 16

the total energy of the system remains constant due to the conservation of energy

Question 17

what is waste energy

Answer 17

the energy that is not used by the device for its desired purpose

Question 18

describe the energy changes that occur in a filament light-bulb

Answer 18

• electrical energy is transferred into light and heat energy
• light is a useful energy form, heat is a waste energy

Question 19

state two equations to calculate efficiency

Answer 19

efficiency = useful output energy transfer / total input energy transfer
efficiency = useful power output / total power output

Question 20

how can the efficiency of a system be increased

Answer 20

1. reducing waste output (by lubrication or thermal insulation)
2. recycling waste output (recycling thermal waste energy as input energy)

Question 21

state the consequence for energy transfer of a material with a high thermal conductivity

Answer 21

the rate of energy transfer through the material is higher than for a material with a lower thermal conductivity

Question 22

do double glazed windows have a higher or lower thermal conductivity than single glazed windows

Answer 22

lower, meaning less energy transfers through them

Question 23

what key factors affect the rate of cooling of a building

Answer 23

1. thickness of walls
2. thermal conductivity of the walls

Question 24

state three methods of reducing heat loss in a building

Answer 24

1. double glazing
2. loft and wall insulation
3. thicker walls

Question 25

how can the efficiency of a mechanical machine with moving parts be improved?

Answer 25

lubricate any moving parts to reuse the friction and therefore energy loss due to heating

Question 26

how can the efficiency of a radiator be improved?

Answer 26

installing metal foil sheets behind the radiator to reflect the heat back into the room rather than it being absorbed into the walls

Question 27

how can the efficiency of boiling water in a pan be improved

Answer 27

by placing a lid on the pan to reduce the heath loss from the top

Question 28

what is a renewable energy resource

Answer 28

an energy source which can be used to replenish as it is being used up.

Question 29

give 4 examples of renewable energy

Answer 29

1. wind energy 2. hydro-energy 3. tidal energy 4. solar energy

Question 30

give an example of non-renewable energy

Answer 30

fossil fuels examples are: coal/oil/gas

Question 31

what are advantages of generating power using gas rather than coal

Answer 31

- flexible generation: gas power stations have short start-up times so can be switched off more easily and regularly - lower emissions of carbon dioxide

Question 32

state 2 disadvantages of renewable energy resources used to generate power

Answer 32

- output often determined by external factors, like wind speed, so supply is not certain - generating power through other means is often more efficient and economically beneficial

Question 33

explain environmental impacts of burning fossil fuels

Answer 33

- carbon dioxide contributes to the greenhouse effect, and causes global warming - sulphur dioxide leads to acid rain, which can damage buildings and crops

Question 34

state 3 advantages of fossil fuels as an energy resource

Answer 34

1. reliable: not dependent on external factors so can generate power at any time 2. can produce large amounts of energy for a given quantity 3. still relatively abundant, so cost efficient

Question 35

state 3 advantages of nuclear power

Answer 35

1. very large amounts of energy for relatively small quantities of fuel 2. doesn't release greenhouse gases so it doesn't contribute to climate change 3. low fuel costs

Question 36

state 3 disadvantages of nuclear power

Answer 36

1. produces nuclear waste which is harmful to humans and must be safely stored for centuries 2. non-renewable energy source 3. risk of nuclear accidents, which have fatal consequences on humans and the environment

Question 37

how does hydroelectric power produce energy

Answer 37

- rainwater collects behind a dam - when this water is released it is used to turn a turbine - this turbine turns a generator which produces electricity

Question 38

what are some disadvantages of using biofuels

Answer 38

- when plants are burned or decay they release CO2 - in order to grow biofuels, you need to destroy land which causes issues like destroying natural habitats, or releasing CO2 - growing biofuels reducing land available growing for food

Question 39

what are advantages of tidal energy sources

Answer 39

- they do not produce greenhouse gases - quite reliable as tides always happen twice a day - cheap to run as tides are natural and are free

Question 40

disadvantages of hydroelectric power

Answer 40

the dam may cause flooding can cost a lot to install the required infrastructure

Question 41

advantages of solar panels

Answer 41

- they don't cause harm to the environment - they are renewable - they can be used in remote areas where other types of electricity is less available

Question 42

examples of a social factor which may act as a deterrent for certain types of energy production

Answer 42

- visual pollution - sound pollution

Question 43

disadvantage of wind farms

Answer 43

- visual pollution - sound pollution