Stopping Distance & Brake Performance Flashcards
7 cards from real Air Brake Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Stopping Distance & Brake Performance flashcards as text
What are the three main components that make up total stopping distance for a vehicle with air brakes?
Answer: Perception distance, reaction distance, and braking distance
Total stopping distance is the sum of perception distance (time to see a hazard), reaction distance (foot moving to brake), and braking distance (vehicle coming to a stop).
Approximately how long is the brake lag time for air brakes compared to hydraulic brakes?
Answer: Air brakes lag about 0.4 seconds vs. 0.1 seconds for hydraulic brakes
Air brakes have a lag of approximately 0.4 seconds because air must travel through the lines to activate the brakes, while hydraulic brakes respond almost instantly at about 0.1 seconds.
At 55 mph on dry pavement, approximately how many feet of additional stopping distance does air brake lag add compared to the moment you press the brake pedal?
Answer: About 32 feet
At 55 mph, a vehicle travels roughly 80 feet per second, so 0.4 seconds of brake lag adds approximately 32 feet before braking even begins.
A fully loaded truck traveling at 55 mph on dry pavement requires approximately how many feet to come to a complete stop?
Answer: About 335 feet
At 55 mph, a fully loaded truck needs roughly 335 feet to stop when accounting for perception, reaction, brake lag, and braking distance on dry pavement.
How does vehicle weight affect stopping distance for air-braked vehicles?
Answer: Empty trucks often take longer to stop than fully loaded trucks due to reduced traction
Empty trucks can require up to 40% more stopping distance than loaded trucks because lighter vehicles have less weight pressing the tires onto the pavement, reducing traction.
Which factor has the GREATEST impact on braking distance when descending a steep grade?
Answer: The grade itself increases the speed and force needed to stop, dramatically lengthening stopping distance
On a downgrade, gravity continuously accelerates the vehicle while brakes must work against both momentum and gravity, significantly increasing the distance needed to stop.
If you double your speed from 20 mph to 40 mph, by approximately how much does your braking distance increase?
Answer: Braking distance increases approximately four times
Braking distance increases with the square of speed; doubling speed from 20 to 40 mph quadruples the braking distance because kinetic energy is proportional to velocity squared.