In a car the brakes stop while friction btn the road surface stop the car .On a wet road the coefficient of kinetic friction between the road surface and the tyres is 0.1.Two cars A and B are travelling at a speed of 15m/s and 30m/s respectively .Brakes are suddenly applied on each of the cars .How far will the cars travel before coming to rest
by the way if you know the energy methods you can say the work done by friction = change of kinetic energy
0.1 m g * x = (1/2) m v^2
x = 5 v^2/g
if v = 15
x = 5*225/g which is 1125/g which is the same as 7.5(150/g)
friction force = -0.1 m g
F = - 0.1 m g = m a
so acceleration = a = -0.1 g
v = Vi + a t
if v = 0
a t = -Vi
if Vi =15
-0.1 g t = -15
t = 150/g
x = Vi t + (1/2) a t^2
x = 15 (150/g) + (1/2)(-.1g)(150^2) / g^2
= 15 (150/g) - 75 * 150 (.1) / g
= 15(150/g) - 7.5 (150/g) = 7.5 (150/g)
now do it using 30 instead of 15 m/s