Storing Energy

Some elastic materials are intended to absorb energy. The more a material is extended, the greater the force required.

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• The energy stored as a material is deformed is represented by the area between the curve and the extension axis.
• If a force F produces an extension e below the limit of proportionality, then the energy stored = 1?2Fe, as shown in the diagram above.
• since F = ke, energy stored = 1?2ke ².

If seat belts and climbing ropes did not stretch, the forces exerted in stopping a person in an emergency would be too great for the body to withstand.