Answer to Question #175336 in Physics for motion

Question

A car travelling at 30m/seconds brought to rest in a distance of 50 meters

1. calculate it acceleration 

2. time taken for it to come to rest 

Answer 1

1)

$$v^2=v_0^2+2as,$$ $$0=v_0^2+2as,$$ $$a=\dfrac{-v_0^2}{2s}=\dfrac{-(30\ \dfrac{m}{s})^2}{2\cdot50\ m}=-9\ \dfrac{m}{s^2}.$$

The sign minus means that the car decelerates.

2)

$$v=v_0+at,$$ $$0=v_0+at,$$ $$t=\dfrac{-v_0}{a}=\dfrac{-30\ \dfrac{m}{s}}{-9\ \dfrac{m}{s^2}}=3.33\ s.$$