Question

Brakes are applied to a car so as to produce retardation of 5m/s². If the car takes 1.5 s to stop after applying the brakes calculate the distance travelled by it?

Answer 1

1) you can do this in two steps or in one step.

deceleration by brakes a = -5m/sec²
time duration of travel t = 1.5 sec
V = U + a t V = 0 as car stopped
0 = U - 5 *1.5 => U = 7.5 m/sec

Distance traveled S = U t + 1/2 a t²
= 7.5 * 1.5 - 1/2 5 * 1.5² = 5.625 meters

You can do this in ONE STEP if you use the formula S = V t - 1/2 a t²
S = 0 * t - 1/2 (-5) 1.5² = 5.625 meters