Answer to Question #347276 in Physics for maria

Question

A motor cyclist travelling at 12m/s decelerates at 3m/s².

a) How long does it take?

b) how far does he travel in coming to rest?

Answer 1

(a)

$$t=\frac{\Delta v}{a}=\frac{-12\;\rm m/s}{-3\:\rm m/s^2}=4\:\rm s$$

(b)

$$d=v_0t+at^2/2\\ =12*4+(-3)*4^2/2=24\:\rm m$$