Jake's driving a car at 20-m/s and sees a deer and slams on brakes to come to a stop.The coefficient of friction between tires and road as tires slide over the road is 0.55. How far will the car slide?

Let the mass of the car be M, so the force due to weight is Mg, where g = 9.81m/s^2 = acceleration of gravity [although sometimes this is approximated as 10m/s^2]. Breaking force = coefficient of friction x weight = 0.55Mg. Acceleration of the car = - Breaking force / M = -0.55g.

If a body has acceleration a and initial speed u, then after displacement s has speed v, then v^2 = u^2 + 2as. When the car stops sliding v = 0, allowing calculation of the sliding distance s according to