# Equations - stress, strain and young's modulus

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## Stress

Stress = Force/area Where force is in N and area is in m^2. Stress is measured in Pascals.

It is used to test how strong a material is - how much pressure a material can withstand before undergoing some sort of physical change.

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## Strain

Strain = extension/length Extension = how much material has stretched (gained in length)

Length = original length

Both the extension and the length must be measured using the same units, but this measurement can be any unit (that measures length). Strain has no units as, for example, 2 metres/ 4 metres = 1/2. Strain is therefore a ratio. It is used to find out how much a material has stretched.

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## Young's modulus

Young's modulus = stress/strain It is measured in pascals as, for example, 50 pascals/2 = 25 Pascals.

Young's modulus is used to measure the stiffness of a material. It is the amount of strain a material undergos when a certain amount of stress is on it.

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