Topic 3 - Conservation Of Energy - Energy Transfers

Question 1

What is the equation for gravity potential energy

Answer 1

Mass x gravitational field strength x height

Question 2

Give the equation for kinetic energy

Answer 2

1
— x mass x (velocity)2
2

Question 3

What is meant by the conversation of energy

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 conversation 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

What is waste energy

Answer 7

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

Question 8

State two equations to calculate efficiency

Answer 8

Efficiency = useful output energy
——————————
Total input energy

Efficiency = useful power output
——————————
Total power output

Question 9

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

Answer 9

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

Question 10

How can you reduce unwanted energy transfer in a mechanical system

Answer 10

Reduce friction by lubricating moving parts