Question

A car is traveling at 55.1 km/h on a flat
highway.
The acceleration of gravity is 9.81 m/s
2. a) If the coefficient of kinetic friction between the road and the tires on a rainy day is
0.116, what is the minimum distance needed
for the car to stop

b) What is the stopping distance when the
surface is dry and the coefficient of kinetic
friction is 0.698

Answer 1

First of all, convert 55.1 km/h to 15.3 m/s

2a) The stopping distance X is given by this equation that relates the kinital kinetic energy to the work done against friction:
(1/2)M V^2 = M*g*Uk*X
Notice that the mass M cancels out, which is good since they did not tell you the mass.

X = V^2/(2*g*Uk) = 103 m

2b) Use the same formula, but with the different value of Uk (the kinetic friction corefficient). The stopping distance is much less.