# Physics Definitions

Definitions of key physics subjects

## Kinetic Energy

Kinetic energy is the energy needed to accelerate a body of a given mass from rest to a stated velocity.

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## Gravitational potential energy

Gravitational potential energy is the energy an object posseses because of its position in a gravitational field.

Weight(N) * Height(m) = Gravitational potential energy(J) = mgh (mass(kg) * gravitational field strength(N/kg) * height(m))

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## Work

Work is the product of a force multiplied by the distance through which it acts.

Work(J) = Force(N) * Distance(m)

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## Power

Power is the rate of energy transfer.

Power(W) = Work(J) * Time(s)

1kg of coal will release more energy than detonating 1kg of TNT as it burns for longer. However detonating 1kg of TNT has a higher power as it releases more energy in a shorter time frame.

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## Efficiency

Efficiency is the percentage of useful work in terms of total work completed.

Efficiency(%) = useful energy output(J) / total energy output(J) * 100%

1st Law: Energy is not created or lost but is only converted from one form to another. The amount of energy is always the same as it is never created or destroyed.

2nd Law: In energy transfer energy speads out and thus becomes less useful to us.

Enegy is also less useful if it is converted to an energy type we don't need.

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