Originally Posted by

**aqua** I do not understand how the question can be solved if I have only been given the times and distances. I thought that you need 3 items.

There are two items to work out so how do I do this with only the distance and time:

*P, Q and R are three points on a straight road, such that PQ=184m and QR=285.75m . A car traveling with constant deceleration passed points P, Q and R at times t=0, t=8 and t=25 seconds respectively. What is the retardation and the velocity of the car at P.*

I know the equations for constant acceleration are:

v=u+at

v^2=u^2+2as

s=0.5(u+v)t

s=ut+0.5 * a * t^2

I tried working out the velocity using distance divided by time but this is average and not useful. I then tried rearranging the equation so a was the subject and then put the two equal to each other which did not work.