While speed, distance and time are the most common compound unit questions you will encounter, You still need to be able to find the others. The one we will focus on here is pressure, force and area
The hardest part of completing questions about Pressure, Force and Area is remembering the formulas.
How to find the formulas.
The easiest way to do this is to memorise the formula triangle. We can then use this to find the formulas.
How do we use this?
Simple, just highlight the thing you are trying to find (I've done it with a red circle) and the formula will be what's left.
Example 1: What is the pressure when a force of 8N is applied to an area of 2m2
The first step in these calculations is always to decide what you are trying to find. For this one, we are directly asked for the volume
P = F ÷ A
Now we can plug in our numbers
V = 8 ÷ 2
The last question that you need to ask is what the units are. The pressure here could be given in N/m2, but could also be given in Pascals (Pa). These are the same unit and ou will get marks either way.
Pressure = 4 Pa
Example 2: The Pressure on an object is 3 Pa and the force being applied is 15 N. What is the area the force is acting on?
Once again, we need to decide which formula. Don't worry that it asks for average density, we can use the same formulas.
A = F ÷ P
Plugging in our numbers gives...
D = 15 ÷ 3 = 5
When you are dealing with pressure, faorce and area, unless you are told otherwise, the units for area will be m2
Area = 5 m2