Recently my A-level mechanics student has had difficulty remembering the SUVAT equations of motions. I wrote a blog entry on these a while ago. I’m now trying to think of an easy way to remember them, which a struggle! The best advice is to use them regularly, or just write them out every day.

a = (v-u)/t – is just the definition of Acceleration

s = (u + v)/2 * t is using the average speed in the old speed * time formula

The other three can be derived from these but in a hurry, better remembered

v^{2 }= u^{ 2} + 2as

s = ut + at^{2}/2

s = vt – at^{2}/2

All of these have different forms where the subject is different, but re-arranging formulas is easier than remembering 20 equations.

There are 5 variables here and five equations.. and each equation has one of the 5 variables missing. This means we can find the other variables with just 3 pieces of information. Just use the equation with the 3 parts you have and the one you are looking for.

*A car travels 20m from a standing start in 10 seconds at constant acceleration. Find this acceleration and the speed after those 10 seconds*

We will work out these things separately with two different equations

The acceleration we can find with the 4th equation – the one without v

10 = 100a/2

This is made easier because the standing start means u =0 and we can disregard the first element

10 = 50a so a = 0.2m/s

We now could use any of the equations to find s as we know everything else, but I do suggest we don’t use a in this calculation,, just in case we didn’t get that right first time – even though I can’;t see any mistake

So we are going to use s = (u + v)/2 * t

20 = v/2 * 10 = 5v

v = 4m/s