Energy

Question 1

What is the equation for gravitational potential energy?

Answer 1

GPE= mgh

Mass x Gravitational Field Strength x Height

Question 2

What is the equation for kinetic energy?

Answer 2

½ mv²

½ x Mass x (Velocity)²

Question 3

What is meant by the conservation of energy? ( 2 points)

Answer 3

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

Question 4

Describe the energy changes involved when a ball is thrown upwards and then returns to its starting position. Ignore air resistance.

Answer 4

● Upwards: KE is converted to GPE
● Peak: Maximum GPE, zero KE
● Downwards: GPE is converted to KE

Question 5

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

Answer 5

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

Question 6

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

Answer 6

● Electrical energy is transferred into light and heat energy
● Light is a useful energy form, heat is waste energy

Question 7

Describe the energy transfers for a bungee jumper.

Answer 7

● When falling, the GPE is converted to KE of jumper
● As the cord tightens, KE is converted and stored as Elastic Potential Energy (EPE)
● At lowest point, the jumper’s initial GPE equals the EPE stored in the cord

Question 8

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

Answer 8

● Kinetic energy decreases since it is converted to elastic potential energy
● Since KE is proportional to (velocity)²,
as KE decreases, so does velocity.

Question 9

What is waste energy?

Answer 9

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

Question 10

State two equations to calculate efficiency.

Answer 10

=Useful Output Energy / Total Input Energy x100

=Useful Power Output/Total Power Output x100

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Lower, meaning less energy transfers through them.

Question 13

State three methods of reducing heat loss in a building.

Answer 13

1. Double glazing
2. Loft and wall insulation
3. Thicker walls

Question 14

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

Answer 14

Reduce friction by lubricating moving parts.

e.g: bike chain

Question 15

How can the efficiency of a system be increased?

Answer 15

1. Reducing waste output
   (by lubrication, thermal insulation etc.)
2. Recycling waste output
   (eg. recycling thermal waste energy as input energy)

Question 16

What is a renewable energy resource?

Answer 16

An energy source which can be replenished as it is being used up. (It never runs out)

Question 17

Give four examples of renewable energy resources.

Answer 17

1. Wind Energy
2. Hydro-Electricity
3. Tidal Energy
4. Solar Energy

Question 18

Give examples of a non-renewable energy resource.

Answer 18

Fossil Fuels (coal, natural gas, oil)
nuclear energy

Question 19

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

Answer 19

● Flexible Generation: Gas power stations have short start-up times so can be switched on/off more readily

● Lower emissions of carbon dioxide

Question 20

State two disadvantages of using renewable energy resources to generate power.

Answer 20

● Output often dependent on external factors (like wind speed), so supply is uncertain

● Renewable fuels often produce less energy per kg (so are less economical).

Question 21

Explain the environmental impacts of burning fossil fuels.

Answer 21

● Carbon Dioxide contributes to the greenhouse effect, and causes global
warming

● Sulphur Dioxide leads to acid rain, which can damage buildings and crops

Question 22

State three advantages of fossil fuels as an energy resource.

Answer 22

1. Reliable: Not dependent on external factors so can generate power anytime
2. Produce large amounts of energy per kg
3. Still relatively abundant, so cost-effective

Question 23

State three advantages of nuclear power.

Answer 23

1. Very large amounts of energy per kg of fuel
2. No greenhouse gases released, so doesn’t contribute to climate change
3. Low fuel costs

Question 24

Give examples of social factors to consider in energy production.

Answer 24

● Visual Pollution
● Sound Pollution

(in wind farms)

Question 24

State three disadvantages of nuclear power.

Answer 24

1. Produces nuclear waste:
   harmful to humans & must be safely stored
   for centuries.
2. It is a Non-Renewable energy source
3. Risk of nuclear accidents:
   fatal consequences on humans and the
   environment

Question 25

What are some disadvantages of using biofuels?

Answer 25

● When plants are burned/decay they release CO2

● In order to grow biofuels, you need to destroy land:
○ Habitat destruction
○ CO2 released when plants are cleared (for example, if they are burned)

● Growing biofuels reduces the land available for food crops

Question 25

How does hydroelectric power produce energy?

Answer 25

● 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 26

What are the advantages of tidal energy sources?

Answer 26

● No greenhouse gases
● Fairly reliable - tides occur twice a day
● Cheap to run as tides are natural, so
free

Question 27

What are the disadvantages of hydroelectric power?

Answer 27

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

Question 28

What are some advantages of solar panels?●

Answer 28

● They don’t cause harm to the
environment

● They are a renewable resource

● They can be used in remote areas where other types of energy are less accessible