Question

A truck of mass 1800kg is moving with a speed of 54Km/h when brakes are applied its stops with uniform negative acceleration at a distance of 200m. calculate the force applied by the brakes of the truck and work done before stopping.

Answer 1

Given mass of truck = 1800 kg
speed = 54 km/hr = 54 * 5/18 m/s = 15 m/s
distance traveled after brakes are applied  = 200 m
final velocity = 0 m/s
From equation of motion ,
v²-u² = 2as
0-15² = -2a × 200
a = 225/400
a = 0.5625 m/s²

force applied by brakes(F) = ma
                                               = 1800 × 0.5625
                                               = 1012.5 N

work done (w) = FS
                         = 1012.5 × 200
                         = 202500 N-m