Question

A motor car weighing 2000kg is moving with a velocity 54 km/hr. Calculate the force necessary to bring it to rest within a distance of 112.5m

Answer 1

given, mass of motor car, m = 2000kg

initial velocity , u =54km/h = 54 × 5/18 = 15 m/s

we have to find force necessary to bring it to rest within a distance of 112.5m

so, distance covered by motor car, s = 112.5 m

final velocity of motor car, v = 0

use formula, v² = u² + 2as

or, (0)² = (15)² + 2a(112.5)

or, -225 = 225a

or, a = -1 m/s² [ negative sign indicates that force force is applied just opposite direction of its motion]

now, from Newton's 2nd law, F = ma

= 2000kg × 1 m/s² = 2000N