AQA GCSE Physics

Revision Notes

5.3.1 Changing Shape

Forces & Changing Shape

  • For stationary objects, more than one force has to be applied to change their shape
  • Their shape can change by:
    • Stretching (forces in opposite directions away from the object)
    • Bending (forces that distort the object)
    • Compressing (forces in opposite directions towards the object)
  • A combination of all three shape changes can also occur

Compression

  • An example of compression is placing a mass on top of a spring placed on a flat surface
  • The two forces are:
    • The weight of the mass
    • The reaction force from the surface to the spring
  • These two forces are towards each other

Compressing and Stretching Spring, downloadable IGCSE & GCSE Physics revision notes

The compression or stretching of a spring requires two forces

Stretching

  • An example of stretching is placing a mass on the bottom of a vertically hanging spring
  • The two forces are:
    • The weight of the mass
    • The tension in the spring
  • These two forces are away from each other
    • These opposite forces are a result of Newton's Third Law

Bending

  • An example of bending is a diving board bending when a swimmer stands at the far end
  • The two forces are:
    • The weight of the swimmer
    • The reaction force from the block to the dividing board
  • These two forces act towards each other, but at different points on the object
  • Bending can also be caused by two forces at an angle to each other

Diving Board Bending, downloadable IGCSE & GCSE Physics revision notes

Forces on a diving board cause it to be bend when a swimmer stands on one end

bending-forces, IGCSE & GCSE Physics revision notes

More than one force on an object can cause it to bend

Elastic & Inelastic Deformation

  • When some objects, such as springs or rubber bands, are stretched they will return to their original shape and length once the forces are removed
    • Other materials, such as plastic, remain permanently distorted (stretched)

Elastic & Plastic, downloadable IGCSE & GCSE Physics revision notes

Elastic materials return to their original shape and size after stretching whilst plastic materials don’t

  • A change of shape is called a deformation and can either be:
    • Elastic
    • Inelastic

Elastic Deformation

  • Elastic deformation occurs:

When objects return to their original shape when the stretching force is removed

  • Examples of materials that undergo elastic deformation are:
    • Rubber bands
    • Fabrics
    • Steel springs

Inelastic Deformation

  • Inelastic deformation occurs:

When objects remain stretched and do not return completely to their original shape even when the stretching force is removed

  • Examples of materials that undergo inelastic deformation are:
    • Plastic
    • Clay
    • Glass

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