# Concept 9: Energy

## Success Criteria

• I can describe different forms of energy and identify energy transformations.

• I can define ‘gravitational potential energy’ and calculate it using the formula EP = mgh.

• I can define ‘kinetic energy’ and calculate it using the forcula EK = ½mv2.

• I can rearrange the formula EP = mgh or EK = ½mv2 to solve a range of problems.

## Vocabulary

Energy

Joule

Transformation

Energy is the capacity to do work. That is, the capacity to exert a force that will cause motion. It is measured in units of Joules (J).

## Kinetic Energy

Success Criteria:
I can define ‘kinetic energy’ and calculate it using the forcula EK = ½mv^2.

Use this equation to calculate kinetic energy.  Kinetic energy is the energy an object has due to its motion.

An object's kinetic energy depends on the object's mass and speed.

• An object with twice the mass but same speed has twice the kinetic energy.

• An object of same mass but twice the speed has four times the kinetic energy. ## Gravitational Potential Energy

Success Criteria:
I can define ‘kinetic energy’ and calculate it using the forcula EK = ½mv^2.

Use this equation to calculate gravitational potential energy.  Gravitational potential energy is the stored energy an object has due to its height above the ground.

• An object with twice the mass but at the same height has twice the gravitational potential energy.

• An object of the same mass but at twice the height has twice the gravitational potential energy.

On Earth, the strength of gravity is approximately 10 N/kg or m/s/s. ## Conservation of Energy

The law of conservation of energy states that:

"Energy cannot be created or destroyed, it can only be transformed from one form to another."  # Concept 10: Work & Power

## Success Criteria

• I can define ‘work’

• I can use the formula W = F x d to calculate work, force, or distance.

• I can define ‘power’.

• I can use the formula P = W/t to calculate power, work, or time.

Energy

Joule

Transformation

## Work

Success Criteria:
I can define 'work'.
I can use the formula W = F x d to calculate work, force, or distance.

The work done when a force moves an object over a distance in the direction of the force can be calculated using this equation:  Work done is the energy transferred when a force moves an object over a distance. Work is only done when the force moves the object. If the object doesn't move, then no work has been done (as no energy has been transferred. The following energy transfers assume no energy is lost to friction: Often, the work done doesn't all go into kinetic or potential energy. Usually, heat is also created due to friction or drag.

## Power

Success Criteria:
I can define 'work'.
I can use the formula W = F x d to calculate work, force, or distance.

The power developed by a transfer of energy in a certain time is given by: Power is the rate of doing work (how quickly energy is transferred). The faster the transfer of energy, the greater the power.   