A car of mass 480 kg moving at a speed of 54 km h-1 is stopped by applying brakes in 10 s. Calculate the force applied by the brakes.

Mass (m) = 480 kg

Initial velocity (u) = 54 km h^-1 or 15 m s^-1

Final velocity (v) = 0

Time (t) = 10 s

Acceleration (a) = 0-15\over 10

⇒ a = – 1.5 m s ^-2

The negative sign shows that it is retardation.

Now,

Force (F) = mass (m) × acceleration (a)

= 480 × 1.5 = 720 N

Hence, The magnitude of force applied by the brakes = 720 N