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• Does a car speed up on ice?

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Does a car speed up on ice?

Question

February 14, 2008

The question I have is simple but I can't prove the answer. If a 3000 pound car is traveling a 60mph, on a flat surface,then hits a sheet of ice. The driver then applies the brakes which in turn lock the tires. Is it possible for the car to increase speed? Why or why not, and what happens to all the friction and energy?
What formulas do I need to prove this?

John - USA

15353

Answer

By the laws of the Conservation of Energy and Conservation of Momentum, the car cannot increase its speed when sliding on ice with the wheels locked. Since no power is applied to the wheels, an increase in speed would mean an increase in energy and momentum, which is not allowed.

With energy: MV^2/2 = mv^2/2. Since the mass is the same M = m, the velocities are the same V = v. Likewise with momentum: MV = mv.

The car will slowly decrease in speed, due to the small coefficient of friction of the ice. Energy is lost through the tires in the friction.

When you slide on ice with your wheels locked, it only feels like you are going faster because you don't feel the subtle vibrations from the wheels rolling on the pavement.

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