EVOC Emergency Vehicle Dynamics & Physics 1 — Questions and Answers
Question 1: When a driver doubles their speed, how does stopping distance change?
- It doubles (2×)
- It triples (3×)
- It quadruples (4×) (Correct answer)
- It increases by 50%
Correct answer: It quadruples (4×)
Stopping distance is proportional to the square of speed, so doubling speed quadruples the stopping distance.
Question 2: What is the correct braking technique for a vehicle equipped with anti-lock brakes (ABS) during an emergency stop?
- Rapidly pump the brake pedal
- Apply firm, continuous pressure and hold (Correct answer)
- Apply, release, and reapply in 2-second cycles
- Use very light, gradual pressure to avoid skidding
Correct answer: Apply firm, continuous pressure and hold
ABS-equipped vehicles require firm, sustained pedal pressure; the system automatically modulates brake force to prevent wheel lockup.
Question 3: Which single factor has the greatest impact on total stopping distance at highway speeds?
- Tire tread depth
- Road surface condition
- Vehicle speed (Correct answer)
- Driver reaction time
Correct answer: Vehicle speed
Since stopping distance increases with the square of speed, vehicle speed has an exponential—not linear—effect on total stopping distance.
Question 4: What causes brake fade during prolonged heavy braking?
- Loss of hydraulic brake fluid pressure
- Overheating of brake components reducing friction effectiveness (Correct answer)
- Air entering the brake lines during compression
- Unequal weight distribution between front and rear axles
Correct answer: Overheating of brake components reducing friction effectiveness
Brake fade occurs when excessive heat builds up in the braking system, lowering the friction coefficient between pads and rotors.
Question 5: How does a heavier vehicle load affect stopping distance?
- Decreases stopping distance due to better tire contact
- Has no effect if tires are properly inflated
- Increases stopping distance due to greater kinetic energy (Correct answer)
- Only affects stopping distance on grades steeper than 6%
Correct answer: Increases stopping distance due to greater kinetic energy
A heavier load increases the vehicle's kinetic energy, which requires more distance and braking force to dissipate.
Question 6: What is the recommended technique to prevent brake fade when descending a steep grade?
- Keep brakes continuously applied at moderate pressure throughout the descent
- Use engine braking by downshifting and apply brakes intermittently (Correct answer)
- Apply full brake pressure periodically, then release completely
- Increase speed to generate air resistance and reduce brake reliance
Correct answer: Use engine braking by downshifting and apply brakes intermittently
Engine braking reduces the workload on friction brakes, preventing heat buildup and brake fade on long descents.
Question 7: At what approximate speed does hydroplaning typically begin on a wet road surface?
- 20 mph
- 35 mph (Correct answer)
- 50 mph
- 65 mph
Correct answer: 35 mph
Hydroplaning can begin at speeds as low as 35 mph when tires lose contact with pavement due to a film of water.
EVOC Emergency Vehicle Dynamics & Physics 1
When a driver doubles their speed, how does stopping distance change?