How does the generation of heat help stop the vehicle?
- Heat melts the tires, increasing their stickiness.
- Heat triggers an automatic vehicle stop system.
- The brake linings rub against the brake drums, creating friction. ✓
- The heat evaporates the brake fluid, increasing brake pressure.
Answer: C. The brake linings rub against the brake drums, creating friction.
The heat comes from friction when the brake linings rub against the brake drums, and that friction converts the vehicle's motion into heat to stop it.
Why this is the answer
The handbook compares vehicle brakes to a rollerblade pad rubbing on pavement. In a drum brake, the linings rub against the drum; in a disc brake, pads rub against the rotor. That rubbing creates friction, and friction changes the vehicle's energy of motion into heat. The brake drums or rotors absorb that heat and release it to the air. The stopping effect comes from this friction and energy conversion, not from the heat doing something separate to the tires or brake fluid.
Why the other answers are wrong
- A. Heat melts the tires, increasing their stickiness. — The passages do not say heat melts the tires or makes them sticky; they describe friction between brake linings and drums or rotors as what slows the vehicle.
- B. Heat triggers an automatic vehicle stop system. — No automatic vehicle stop system is mentioned; the passages say braking comes from friction in the brake components.
- D. The heat evaporates the brake fluid, increasing brake pressure. — The passages do not mention heat evaporating brake fluid or increasing brake pressure; they say heat is absorbed and dissipated through the brake drums or rotors.
Remember it
Picture the brake drum or rotor as the place where motion is turned into heat, not as something that changes the tires.