1. IP2.11.3 Forces can change the shape of objects © Oxford University Press 2011 Forces can change the shape of objects

2. IP2.11.3 Forces can change the shape of objects © Oxford University Press 2011  Forces acting on an object can change their shape as well as make them accelerate.  Forces can stretch or squash objects.  A lot of the time forces that change the shape of an object are destructive. Think of car accidents or someone breaking a chair leg. These forces have all squashed or stretched material to breaking point.  However, forces changing the shape of an object can also be put to good use.  Can you think of some applications where forces squashing or stretching an object is useful?

3. IP2.11.3 Forces can change the shape of objects © Oxford University Press 2011  When a spring is squashed or stretched by a force, energy is transformed into elastic potential energy and stored within the spring. (We can say that work has been done on the spring.)  When the force is removed, this energy is converted into other forms which return the spring to its original length.  The same thing happens when you pull back an elastic band. This process of storing elastic potential energy is useful for spring toys, wind-up clocks and vehicle suspension systems.

4. IP2.11.3 Forces can change the shape of objects © Oxford University Press 2011 Can you think of objects that use this ability to store elastic potential energy? Toys store energy in coiled up springs Old wind-up clocks store energy in coiled up springs Shock absorbers on cars store energy when the car hits a bump and then return the spring to its original length, smoothing out the ride for the passengers.