Exercise 4 - Speed, Forces, Friction and Pressure     (Worksheet 3)     Answers

Pressure

Pressure is a measure of how concentrated or spread out a force is.

If a force is applied over a small area it creates a large pressure.
Alternatively, if a force is applied over a large area it creates a small pressure.

Examples of this phenomenon are present in every aspect of life.

Consider pushing a drawing pin into a wall. The area is incredibly small (the sharp point of the drawing pin) and hence the pressure will be large. Consider a skier. If the skier is walking in the snow, his feet will sink quite quickly. However if he is wearing skis, he will be able to glide on the snow instead. This is due to the area of the skis being considerably larger than that of the skier's shoes. Hence the pressure is larger on the small area (the skier's shoes) and the skier sinks into the snow.

We are able to calculate the pressure created by a force using the following equation:

Pressure is measured in Pascals (Pa).

(remember area = breadth x length).

If drawn as a formula triangle, this formula would appear as:
 

F = Force   P = Pressure   A = Area

Using the formula above we can consider the following question.

A crate weighing 500 N is standing upright on one of its sides, which measures 2 m x 2m. Calculate the pressure created by the crate.

To answer this question we must firstly consider the area of the crate.
The area is 2m x 2m = 4m².

Now we know the area we can apply the rest of the formula for pressure.

Pressure = Force = 500 = 125 Pa.
Area 4

The correct answer is 125 Pa.
 

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