3.4.1.8 Conservation of Energy

Question 1

What is energy needed to do?

Answer 1

Energy is needed to make stationery objects to move, to change their shape, or to warm them up.

Question 2

Name the 4 energy stores and which type of objects store the type of energy.

Answer 2

Gravitational Potential - The position of objects in a gravitational field.
Kinetic - Moving objects.
Thermal Stores - Hot objects.
Elastic Potential - Objects being compressed or stretched.

Question 3

Name the 3 Energy Transfers and give examples.

Answer 3

Radiation - e.g. light.
Electrically - e.g. charge carriers around a circuit as potential difference.
Mechanically - e.g. sound.

Question 4

What does the law of conservation of energy state?

Answer 4

Energy cannot be created or destroyed, it can be only be transferred from one form to another.
The total amount of energy in a closed system will not change.

Total Energy In = Total Energy Out.

Question 5

What is efficiency?

Answer 5

A measure of how well a system transfers energy,

Question 6

What is the equation for efficiency (in terms of energy)?

Answer 6

Efficiency = Useful output Energy / Total energy input.

Question 7

What is the equation for efficiency in terms of power?

Answer 7

Efficiency = Useful Power output / Total power input.

Question 8

What is the equation for kinetic energy?

Answer 8

Kinetic Energy = 1/2 x mass x velocity^2

Question 9

What is the equation for gravitational potential energy?

Answer 9

Gravitational Potential Energy = Mass x Gravitational Field Strength x Height.

Question 10

What is the equation for Elastic Potential Energy?

Answer 10

Elastic Potential Energy = 1.2 x Spring Constant x Extension^2