# Physics - Roller Coasters and Relativity

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• Created by: Elliza
• Created on: 02-06-11 20:30

## The Principle of the Conservation of Energy

Energy conservation means using less fossil fuels etc.

However, the principle of the conservation of energy is a different story. Without it, life as we know it would cease to be. The principle is:

Energy can never be created nor destroyed - only converted from one form to another

It is the principle behind how we get electricity, as much electricity comes from burning fossil fuels etc -- the energy is just converted into a different form.

Gravitational potential --> kinetic energy...Also:

Energy is only useful when it's converted from one form to another

Calculating the Speed of Falling objects

When something falls, it's potential energy is converted into kinetic energy. This means it loses potential energy and gains kinetic energy. Therefore:

potential energy lost = kinetic energy gained.

(Example is on back of card)

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## Kinetic Energy Example

Example: A mouldy tomato of mass 140kg is dropped from a height of 1.7m. Calculate it's speed as it hits the floor.

Answer: There are four key steps to this method.

1) Find the PE lost: PE = mgh = 0.14 x 10 x 1.7 = 2.38 J <-- This is also the KE gained/

2) Equate the number of joules of KE gained to the KE formula with v in:

3) Stick the numbers in