Question

On a level road, a scooterist applies brakes to slow down from a speed of 10 m/s to 5 m/s. If the mass of the scooterist and the scooter be 150kg, calculate the work done by the brakes.

Answer 1

Mass of scooter + scooterist = 150 kg 

Initial velocity, u = 10 m/s 

Final velocity, v = 5 m/s 

Retardation = a 

Distance travelled = s 

Using third equation of motion,

v² – u² = 2as 

as = -75/2 

Work done, W = Fs 

W = mas 

W = -5625 J 

Negative sign is used to show that force applied by the brakes is acting opposite direction of motion.