What factor ultimately determines a vehicle's stopping power?

The stopping power of a vehicle is primarily determined by the friction created between the brake linings and the drum. When the brake pedal is engaged, the brake linings press against the drum, generating friction. This friction is what slows down or stops the vehicle. The effectiveness of this friction is influenced by the material of the brake linings, their condition, and the surface of the drum, all of which directly affect how efficiently the braking system can convert the vehicle's kinetic energy into heat and stop the vehicle.

While the weight of the vehicle, road conditions, and speed also play significant roles in the overall stopping distance and vehicle control, the fundamental mechanism that translates brake application into stopping power is the friction between the brake components. Therefore, without sufficient friction, regardless of weight or speed, a vehicle will not stop effectively.