[7] Work, Energy and Power

Question 1

What is the formula for gravitational potential energy?

Answer 1

Ep = mgh

Question 2

What is the formula for kinetic energy?

Answer 2

Ek = 1/2 mv^(Squared)

Question 3

What is the formula for work done?

Answer 3

W = Force overcome x Distance moved in direction of force

Question 4

Recite the Law for the Conservation of Energy

Answer 4

Energy cannot be destroyed, it is always conserved

Also, energy cannot be created or destroyed

Energy is continually being transferred from one form to another, but ultimately all energy transfers result in the surroundings being heated (e.g as a result of doing work against friction) and the energy is ‘wasted’.

Question 5

What is the formula for power?

Answer 5

Power = Work done / Time taken

Question 6

What is the formula for efficiency?

Answer 6

Efficiency = Useful Energy output / Total Energy input

Or

Efficiency = Useful Power output / Total Power input

Question 7

Why is it that efficiency does not have a unit of measurement?

Answer 7

Efficiency is a ratio

Question 8

Why is it that in actual terms, the efficiency of a device or machine will always be less than 1 or 100%?

Answer 8

As energy is always converted into forms which are not wanted often through friction between moving parts which leads to conversion of the input energy to internal energy and heat energy.

Question 9

Why is it that the efficiency of a device or machine cannot be above 1 or 100% ?

Answer 9

As energy cannot be created or destroyed, so the output useful energy can never be greater than the total input energy.

Question 10

In the equation F x S = 1/2 MV^(Squared)

In terms of proportionality, if F and M are constants then …

Answer 10

S ➰ V^(Squared)

Question 11

Non-renewable energy source definition

Answer 11

A non-renewable energy source is a source that will run out or will not be replenished in our lifetimes - or even in many lifetimes.

Question 12

Examples of non-renewable energy sources

Answer 12

Fossil Fuels e.g Coal
Oil
Natural Gas
Nuclear Fuels

Question 13

Renewable energy source definition

Answer 13

Renewable energy is energy that is collected from renewable resources, which are naturally replenished on a human timescale.

Question 14

Examples of Renewable Energy Sources

Answer 14

Biofuel
Biomass
Geothermal
Hydropower
Solar power
Tidal power
Wave power
Wind power