3. Pressure
An equation & units for pressure P.7 of 13

 What is pressure? Pressure is how much force there is on a given area. So, whilst an elephant weighs more than a horse, the horse pushes down with a bigger pressure. This is because the areas of their feet are different. Pressure depends on two variables: force and area (see page 6). They make an equation as follows:
An equation for pressure
 Picture 3.2 An equation for pressure.
Picture 3.2 shows the equation for pressure. The force is on the top of the fraction. Therefore a bigger force will produce a bigger pressure - which is what we expected. Area is on the bottom of the fraction so a bigger area will produce a smaller pressure.
What are the units?
We usually measure force in newtons (N) and area in square centimetres (cm2). The unit for pressure will then be N/cm2. Notice that we get the new unit by putting the old units into the equation (newtons ÷ centimetres squared = N/cm2).
The pascal
The pascal (Pa) is a standard unit for pressure. One pascal is equivalent to 1 N/m2. So, to get the pressure in pascals, you need to measure the force in newtons and the area in square metres (rather than square centimetres).

Question 7
Look at the examples below. In each case work out the pressure.
 Description Pressure A. A woman weighs 600 N and the total area of her high heels is 20 cm2. N/cm2 B. An elephant weighs 12,000 N and the total area of its feet is 1,500 cm2. N/cm2 C. A digger has a weight of 40,000 N. The area of its tracks is 8,000 cm2. N/cm2 D. An arctic explorer weighs 600 N. She wears snow shoes with an area of 1200 cm2. N/cm2 E. Which one will sink into the ground: i)  the most please choose A B C D ii) the least please choose A B C D

 Summary                                           Close pressure is the force per unit area we measure pressure in pascals (Pa) pressure = force ÷ area 1 Pa = 1 N/m2