Topic 3 - Conservation of energy

Question 1

What is the equation for gravitational potential energy?

Answer 1

Mass x gravitational field strength x height

Question 2

What is the equation for kinetic energy?

Answer 2

1/2 x mass x velocity^2

Question 3

What is meant by the conservation of energy?

Answer 3

The total amount of energy in a closed system remains constant
Energy cannot be created or destroyed but can change from one form to another

Question 4

Describe how the the energy changes involved when a ball is thrown upwards and then Returns to its starting position

Answer 4

Upwards : KE is converted to GPE
Peak: maximum GPE, zero KE
Downwards: GPE is converted to KE

Question 5

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

Answer 5

Electrical energy is transferred into light and heat energy

Light is a useful energy form, heat is waste energy

Question 6

Describe the energy transfers for a bungee jumper

Answer 6

When falling, GPE is converted to KE of jumper
As cord tightens, KE is converted and stored as EPE
At lowest point, the initial GPE equals the EPE stored in the cord

Question 7

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

Answer 7

Kinetic energy decreases since it is converted into elastic potential energy
Since KE is proportional to velocity^2, as KE decreases, so does velocity

Question 8

What is waste energy?

Answer 8

The energy that is not used by the device for its desired purpose, or not converted into the desired form

Question 9

State two equations to calculate efficiency

Answer 9

Useful energy output/total input energy

Useful power output/total power output

Question 10

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

Answer 10

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

Question 11

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

Answer 11

Lower, meaning less energy transfers through them

Question 12

State three methods of reducing heat loss in a building

Answer 12

Double glazing
Thicker walls
Loft and wall insulation

Question 13

How can you reduce unwanted energy transfer in a mechanical system?

Answer 13

Reduce friction by lubricating moving parts

Question 14

How can the efficiency of a system be increased?

Answer 14

Reducing or recycling waste output

Question 15

What is a renewable energy resource?

Answer 15

An energy source which can be replenished as it is being used up

Question 16

Give four examples of renewable energy resources

Answer 16

Wind energy
Hydro-electricity
Tidal energy
Solar energy

Question 17

Give an example of a non-renewable energy source

Answer 17

Fossil fuels

Question 18

What are the advantages of generating power using gas rather than coal?

Answer 18

Lower emissions of carbon dioxide

Flexible generation: gas power stations have short start-up times so can be switched on/off more readily

Question 19

State two disadvantages of using renewable energy resources to generate power

Answer 19

Renewable fuels often produce less energy per kg (so are less economical)
Output is often determined by external factors, so supply is uncertain

Question 20

Explain the environmental impacts of burning fossil fuels

Answer 20

Carbon dioxide contributes to the greenhouse effect, and causes global warming
Sulphur dioxide leads to acid rain, which can damage buildings and crops

Question 21

State three advantages of fossil fuels as an energy resource

Answer 21

Produce large amounts of energy for Kg
Still relatively abundant, so cost effective
Reliable: not dependent of external factors so can generate power anytime

Question 22

State three advantages of nuclear power

Answer 22

Very large amounts of energy per Kg of fuel
No green house gases released, so doesn’t contribute to climate change
Low fuel costs

Question 23

State three disadvantages of nuclear power

Answer 23

Produced harmful nuclear waste
Non-renewable energy source
Risk of nuclear accidents, which have fatal consequences for humans and the environment

Question 24

Give examples of social factors to consider in energy production

Answer 24

Visual pollution

Sound pollution

Question 25

How does hydroelectric power produce energy?

Answer 25

Rainwater collects behind a dam
When this water is released, it it used to turn a turbine
This turbine thorns a generator which produces electricity

Question 26

What are some disadvantages of using biofuels?

Answer 26

When plants are burned/decay they release CO2
In order to grow biofuels, you need to destroy land:
Habitat destruction
CO2 release
Growing biofuels reduces the land available for food crops

Question 27

What are the advantages of tidal energy sources?

Answer 27

No greenhouse gases
Fairly reliable
Cheap to run as tides are natural, so free

Question 28

What are the disadvantages of hydroelectric power?

Answer 28

The dam may cause flooding

It can cost a lot to install the required infrastructure

Question 29

What are some advantages of solar panels?

Answer 29

They don’t cause harm to the environment
Are a renewable resource
Can be used in remote areas where other types of energy are less accessible