1. Energy

Question 1

What is the equation for kinetic energy? Give SI units for all quantities involved.

Answer 1

½ m v² (½ x Mass x (Velocity)²); Energy (J), Mass(kg), Velocity(m/s)

Question 2

What is the equation for elastic potential energy? Give SI units for all quantities involved.

Answer 2

½ k x² (½ x Spring Constant x (Extension)²); Energy (J), Spring Constant (N/m), Extension(m)

Question 3

What is the equation for gravity potential energy? Give SI units for all quantities involved.

Answer 3

mgh (Mass x Gravitational Field Strength x Height); Energy (J), Mass(kg), Gravitational Field Strength (N/kg), Height (m)

Question 4

Define the ‘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

J/°C/kg (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 two equations for power. Give SI units for all quantities involved.

Answer 7

power = energy transferred/time; power = work done/time; Energy (J), Work Done (J), Time (s)

Question 8

What is the unit of power?

Answer 8

Watt (W)

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 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 its starting position. Ignore air resistance.

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 the jumper; As the cord tightens, KE is converted and stored as Elastic Potential Energy (EPE); At the lowest point, the jumper’s initial GPE equals the EPE stored.

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)², as KE decreases, so does velocity.

Question 13

Give examples of chemical energy stores.

Answer 13

Food, Fuel (e.g. wood, coal, petrol), Batteries

Question 14

State 4 different stores of energy.

Answer 14

1. Kinetic Energy; 2. Gravitational Potential Energy; 3. Elastic Potential Energy; 4. Chemical Energy

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 any changes in the total energy of a ball that is kicked

Answer 16

assuming that no external forces act.

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 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, thermal insulation, etc.); 2. Recycling waste output (e.g. 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 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

The thickness of the walls, The 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

What is a renewable energy resource?

Answer 25

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

Question 26

Give four examples of renewable energy resources.

Answer 26

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

Question 27

Give an example of a non-renewable energy resource.

Answer 27

Fossil fuels (e.g. coal, oil, and gas).

Question 28

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

Answer 28

Flexible Generation: Gas power stations have short start-up times, so can be switched on/off more readily; Lower emissions of carbon dioxide.

Question 29

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

Answer 29

Output often determined by external factors (like wind speed), so supply is uncertain; Generating power through other means is often more efficient and economically beneficial.

Question 30

Explain the environmental impacts of burning fossil fuels.

Answer 30

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

Question 31

State three advantages of fossil fuels as an energy resource.

Answer 31

1. Reliable: Not dependent on external factors, so can generate power anytime; 2. Can produce large amounts of energy for a given quantity; 3. Still relatively abundant, so cost-effective.

Question 32

State three advantages of nuclear power.

Answer 32

1. Very large amounts of energy for relatively small quantities of fuel; 2. Doesn’t release greenhouse gases and so doesn’t contribute to climate change; 3. Low fuel costs.

Question 33

How does hydroelectric power produce energy?

Answer 33

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 34

What are some disadvantages of using biofuels?

Answer 34

When plants are burned or decay they release CO2; Destroying land to grow biofuels can reduce habitats; Growing biofuels reduces the land available for growing food.

Question 35

What are the advantages of tidal energy sources?

Answer 35

They do not produce greenhouse gases; They are quite reliable as tides happen twice a day; They are cheap to run since tides are natural.

Question 36

What are the disadvantages of hydroelectric power?

Answer 36

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

Question 37

What are some advantages of solar panels?

Answer 37

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.

Question 38

Give an example of a social factor which may act as a deterrent for certain types of energy production.

Answer 38

Visual Pollution; Sound Pollution (both are disadvantages of wind farms).