P1

Question 1

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

Answer 1

½ m v?

½ x Mass x (Velocity)?

Energy (J), Mass(kg), Velocity(m/s)

Question 2

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

Answer 2

½ k x^2

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 Sl units for all quantities involved.

Answer 3

Mass × 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

The energy transferred is the same but the time taken is less (P=E/t).

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

What is gravatational potential

Answer 11

the energy possessed or acquired by an object due to a change in its position when it is present in a gravitational field

Question 12

What is kinetic energy

Answer 12

the energy an object has because of its motion

Question 13

What is Elastic potential energy

Answer 13

energy stored as a result of applying a force to deform an elastic object

Question 14

Describe the energy transfers for a bungee jumper.

Answer 14

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 15

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

Answer 15

• 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 16

Give examples of chemical energy stores.

Answer 16

• Food

• Fuel (eg. wood, coal, petrol)

• Batteries

Question 17

State 4 different stores of energy.

Answer 17

1. Kinetic Energy
2. Gravitational Potential Energy
3. Elastic Potential Energy
4. Chemical Energy
5. Magnetic
6. Electrostatic
7. Nuclear

Question 18

State the law of energy conservation.

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is waste energy?

Answer 20

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

Question 21

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

Answer 21

• Electrical energy is transferred into light and heat energy

• Light is a useful energy form, heat is waste energy

Question 22

State two equations to calculate efficiency.

Answer 22

=Useful Output Energy Transfer/Total
Input Energy Transfer

=Useful Power Output/Total Power
Output

Question 23

What is a chemical energy store

Answer 23

The energy stored in chemical
bonds between molecules

Question 24

Examples of chemical energy stores

Answer 24

Food,batteries,fuel,Muscles

Question 25

What is kientic energy

Answer 25

The energy of moving object

Question 26

What id the Gravitianl potential energy

Answer 26

The energy of an object at height

Question 27

How can the efficiency of a system be increased?

Answer 27

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

Question 28

What is waste output

Answer 28

unwanted or unusable materials

Question 29

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

Answer 29

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

Question 30

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

Answer 30

Lower, meaning less energy transfers through them.

Question 31

What key factors affect the rate of cooling of a building?

Answer 31

• The thickness of the walls
• The thermal conductivity of the walls

Question 32

State three methods of reducing heat loss in a building.