IP2.11.3 Forces can change the shape of objects

© Oxford University Press 2011

Forces can change the shape of objects

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? 

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.

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 springsOld 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.