The faster you are traveling, the more friction you will need to stop.

• A. the same amount
• B. more friction
• C. less friction
• D. no friction

Answer: (B)

When you need to stop, the braking force that acts to slow you down must remove your kinetic energy. To stop from a higher speed, you must decelerate more quickly, so the frictional force available to do that braking must be larger.

A useful way to see this is the work-energy idea: the work done by friction equals the change in kinetic energy. If you want to stop within a fixed distance, the required friction force grows with the square of your speed (F_f × d = 1/2 m v^2). Similarly, the needed deceleration is a = v^2/(2d), and the braking force is F = m a, so F scales with v^2 for a given stopping distance.

So, as speed increases, more friction is needed to stop in the same distance. If surface friction is limited, you’ll either need more distance to stop or accept less-than-ideal stopping performance.