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# Measuring Pressure

## Summary

Students can measure the pressure exerted by familiar objects.

## Operation

Pressure is equal to force divided by area:

P=f/a

Many of you may have heard of the tale that the pressure exerted by a high-heel shoe is more than an elephant’s foot. Well it’s true. Because the elephant’s foot has a greater surface area than the heel of the shoe, even though the elephant weighs a lot more than the wearer of the shoe, it exerts less pressure. This is because the force of the elephant divided by the area of its foot equals less than that of the shoe and wearer.

Teachers may use this equipment as a demonstration rather than a full class practical because of the nature of the objects involved.

A variety of objects (a high-heeled shoe, drawing pins, a hammer, knife, a chisel etc) are shown to the class and the pressure they exert under normal use is discussed.

Pupils can be shown that a drawing pin can easily be pushed into a piece of wood yet a finger cannot even if you exert a greater force. Similarly a blunt and sharp knife can be compared cutting through a material. The sharper knife will have a smaller surface area and so can cut easier.

## Safety

Take care with sharp tools.

The contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.