In how many ways does friction help your vehicle to stop?

• A. Four
• B. One
• C. Two
• D. Three

Answer: (C)

The ability to stop a car relies on friction converting the car’s motion into heat and providing a force opposite to its motion. There are two separate friction-based parts involved.

First, the braking system uses friction between the brake pads and rotors to slow wheel rotation. This is where most of the energy is dissipated as heat, directly reducing how fast the wheels turn.

Second, the tires must grip the road. The friction between the tire rubber and the road surface translates the braking torque into a backward force on the car, producing actual deceleration of the vehicle’s motion.

Together, these two friction interactions—brake-pad/rotor friction and tire-road friction—are the two ways friction helps a vehicle stop.