Pressure
Pressure – force per unit area.
The following equation can be used to calculate pressure (P):
Where F is the force measured in Newtons (N) and A is the area measured in metres squared (m2).
The SI units for pressure is the Pascal (Pa).
Pascal – one pascal is a force of one newton spread evenly over an area of 1 metre squared.
Density
Density – mass per unit volume.
The following equation can be used to calculate density (ρ):
Where m is the mass measured in kilograms (kg) and V is the volume measured in cubic metres (m3).
The SI unit for density is kilogram per cubic metre (kg m-3).
Worked Examples
Example 1
A force of 15N is exerted on an object. The pressure on the object is 50Pa. Calculate the area of the object.
Example 2
A steel ball has a volume of 0.025m3. Calculate the mass of the ball.
The density of steel is approximately 8,000kg m-3.
Example 3
A snowboarder with a mass of 60kg is standing on a snowboard with a surface area of 0.45m2. Calculate the pressure on the snow if the person is standing still. Assume the weight of the snowboard itself is negligible and that the weight of the person is distributed evenly across the snowboard.
This question requires knowledge of weight. Use g = 9.81ms-2.
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