A car that weifgs 15000 n is initially moving at 60 km/hr when the brakes are applied. The cae is broight to a stop in 30 m. Assuming the force applied by the brakes is constant, determine the magnitude of the braking force.

Answer 1

Vo = 60km/hr = 60000m/3600s = 16.67 m/s.

V^2 = Vo^2 + 2a*d
a = (V^2-Vo^2)/2d
a = (0-(16.67)^2)/60 = -4.63 m/s^2.

Wt. of car = m*g = 15000 N.
mass = 15000/9.8 = 1531 kg

F = m*a = 1531 * -4.63 = -7.1 N.