Question

Did you mean: A car of mass 500 kg is moving with a velocity of 36 km/h. when brakes applied it stops with uniform negative acceleration at a distance of 150m.calculate the force applied by the brakes of the car and work done before stopping.

Answer 1

Mass of the car m = 500 kg
Initial speed u = 36 km/h = 10 m/s
Final speed v = 0
s = 150 m
We have v2 - u2 = 2as
a = (v² - u²)/(2s)
= (0 - 10²)/300 = -100/300 = - 0.33 m/s²
Retardation = 0.33 m/s²
Force applied by the brakes = Retarding force F = mass x retardation = 500 x 0.33 = 165 N.
Work done before stopping W = Force x distance moved = 165x 150 = 24750 Nm = 24750 J

Answer 2

Hi there !!

Mass of the car = m = 500 kg

Initial velocity =  u = 36 km/h = 36 × 5/18 = 10 m/s

Final veloicity =  v = 0

Distance = s = 150 m

We know that ,
a = acceleration

v² - u² = 2as

a  = $\frac{ v^{2} - u^{2} }{2s}$
   
    = $\frac{0 - 10^{2} }{2*150}$
   
    = $\frac{-100}{300}$

    = - 0.33 m/s²

Retardation = 0.33 m/s²

Force applied by the brakes =   mass × retardation = 500 × 0.33 = 165 N.

Work done before stopping , W = F × s 
                                                  = 165 × 150
                                                  = 24750 J