1.1 ENERGY CHANGES IN A SYSTEM

Question 1

What is the equation for kinetic energy?

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?

Answer 2

½ k e2
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?

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/kg°C

Joules/Degree Celsius x 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.

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 (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

Describe the energy transfers for a bungee jumper.

Answer 11

● 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 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 (eg. 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