Question

A 2500 kg car is moving at 20 m/s when brakes are applied. If the average force exerted by the brakes is 5000 N, find the distance travelled by the car before it comes to rest?

Answer 1

Mass (m) = 2500 kg

Initial velocity (u) = 20 m/s

Final velocity (v) = 0 m/s [will come at rest]

Force exerted by the brakes (F) = - 5000 N (opposes direction of motion)

We know,

s = (v² - u²)/2a (for that, we have to calculate 'a')

& F = ma

⇒ a = F/m = (- 5000 kg m/s²)/(2500 kg) = - 2 m/s²

∴ s = [- (20 m/s)²]/[- 2 m/s²]

⇒ s = (400 m²/s²)/(2 m/s²)

⇒ s = 200 m