Pressure
What is Pressure?
Pressure is a measure of the amount of force in a given area. For example; the pressure of a finger pushing a wall is fairly small. However, the pressure of a finger pressing a pin against a wall is very high: even though the force is the same. This is because we have reduced the area by alot.
In order to calculate pressure, we use the below equation, which should be very easy to use:
Example: Standing On One Foot
To help you understand how to calculate pressure, we have got a fun little example for you below. Simon is standing on one leg, you are given his mass and the rough size of his feet (he has quite large feet).
Firstly we need to convert his mass into a weight. Using a value of g=10 he weighs 750N, this is the force.
The area of the foot is 20cm x 8cm = 160cm2. Since there are 10 000cm2 in 1m2 this means the area of one foot is 0.016m2.
Now to calculate the pressure in Pascals the force is divided by the area; 750 / 0.016 = 43 750Pa or 43.75 kPa
Gas Pressure
Gas particles are always moving, and in a completely random fashion.
When in a container they will collide with its walls. These collisions are what cause gas pressure. This can be increased by:
The mathematical relationship between volume and pressure change (at a constant temperature) is as follows:
P1 x V1 = P2 x V2