# Energy

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## Working Hard!

work is done and energy is transferred whenever a force moves

Equation For Work Done:   Work Done(J) = Force (N) x Distance moved in direction of force (m)

EXAMPLE: A person lifts a 60n parcel by 1.5m. work done is 60N x 1.5m = 90J

A smaller force is needed to drag something up a ramp compared with lifting it directly up. the force along the ramp is working over a long distance, and also needs to work against friction.

Remember! the force must move in order to do work. A person lifting a box does work but when he is just standing with the box he is doing no work because he is not moving.

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## Gravitational Potential Energy!

Gravitational energy is energy an object has due to its position.The object gains more energy when it is lifted higher above the ground

Equation: Gravitational Potential Energy (joules) = mass (Kg) x Gravity (10N/Kg) x Height (m)

EXAMPLE: The gravitational potential energy gained by a 3kg rabbit lifted 0.8m by its owner is; 3 x 10 x 0.8 = 24J

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## Investigating Kinetic Energy!

All moving objects have kinetic energy, Kinetic energy is calculated using:

• Kinetic energy (J) = 1/2 x mass (kg) x velocity(squared) (M/S)
• EXAMPLE: Kinetic energy of a person (mass 100Kg) running at 3 m/s is 1/2 x 100 x 3(squared) -450J

The Kinetic energy of an object:

• doubles if mass doubles
• quadruples if the speed doubles

At its highest point, a pendelum has a gravitational energy and no kinetic energy, as it swings down some gravitational energy changes to kinetic energy and back again!

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