Unit 1.7 - energy, work and power

What is energy ?

The capacity for doing work

What is kinetic energy?

Energy stored in a moving object

What is gravitational potential energy?

The energy stored by an object due to its height or position. The higher an object off the ground, the greater the energy

What is chemical energy?

The energy stored in chemical bonds

What is elastic energy (strain)

The energy stored when a object is squashed or stretched

What is nuclear energy?

The energy stored in the nucleus of an atom?

What is electrostatic energy?

The energy stored when like chargers are moved closer or unlike charges are moved further apart

What are the 4 types of energy transfer?

Energy can not be created or destroyed and can only be transferred in these ways:

• Mechanical work done

• Electrical work done

• Heating

• Waves

How do you transfer energy through mechanical work done?

This is when a force moves an object through a distance

How is energy transferred through electrical work done?

This is when the charges move due to a potential difference

How do you calculate kinetic energy

All moving objects have kinetic energy, it depends on the mass and speed:

Ek = ½ x m x v²

Kinetic energy is measured in joules

How do you calculate gravitational potential energy?

You can use principal of the conservation of energy to calculate what happens when energy is transferred from a kinetic to gravitational store.

MgΔh = ½ mv²

Name the most common energy resources

• Fossil fuels

• Biofuels

• Wind

• Water energy

• Sun energy

• Geothermal

• Nuclear fuel

What is work?

Work is what is done when the application of a force results in momentum

Work can only be done if an object or system has energy

How do you calculate work done?

Work done = force x distance moved in the direction of the force = energy transferred

W = f x d = ΔE

What is power?

It is defined as the work done per unit time or the energy transferred per unit time

How do you calculate power?

Power = work done / time taken = energy transferred / time taken

P = w / t = ΔE / t

How do you calculate efficiency?

Efficiency = useful energy output / total energy input x 100%

Or

Efficiency = useful power output / total power input x 100%