When a motor vehicle is driven downhill for an extended period, continuous braking generates intense friction between the brake pads and rotors. This friction creates extreme thermal energy that transfers directly into the brake calipers and brake fluid. If the brake fluid exceeds its boiling point, small pockets of vapor form within the hydraulic lines. Because vapor can be compressed much more easily than liquid fluid, the hydraulic pressure drops significantly, which causes the brake pedal to feel spongy and severely reduces stopping power.
According to the passage, what directly causes the brake pedal to feel spongy and lose stopping power?
- AThe friction from the rotors directly pushing compressed air into the pedal
- The formation of easily compressed vapor pockets when the brake fluid boilsAnswer
- CThe spongy pedal compressing the brake fluid and forcing it to overheat
- DThe complete failure of the vehicle's electronic anti-lock braking sensors
Answer
The formation of easily compressed vapor pockets when the brake fluid boils
The passage explicitly explains that when brake fluid boils, vapor pockets form in the hydraulic lines; because vapor compresses much more readily than liquid, hydraulic pressure drops, creating a spongy pedal and reducing stopping power.
Step-by-Step Solution
Key Concept
Identifying explicit cause-and-effect relationships signaled by causal indicators in informational text
Estimated Time:45s