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So I don't know how to copy and paste the table from the passage, but if anyone that has access to TBR CBTs can tell me why using the formula v(final)^2=v(initial)^2+2ad wouldn't lead to the correct answer, I'd greatly appreciate it. I've pasted the question with it's explanation below.
23. At what initial velocity is the braking distance of the test vehicle equal to 100 meters, if the acceleration is -10 m/s2?
A. 38 m/sec
B. 44 m/sec
B is the best answer. Braking distance = Stopping distance Reaction distance. With a braking deceleration of 10 meters per second squared, the stopping distance at 40 meters per second is 110.0 meters, and the reaction distance is 30.0 meters (calculated from 40 m/s x 0.75 s), so the braking distance is 80.0 meters. At a velocity of 45 meters per second, the stopping distance is 135.0 meters, while the reaction distance is 33.75 meters, and the braking distance is therefore 101.25 meters. This means that for a braking distance of 100 meters, the velocity must be just less than 45.0 meters per second, making choice B the best answer. A very easy mistake to make is to read only the chart of stopping distances, and not to note that the question was asking about braking distance. This would have led you down a path of error, so that you would mistakenly choose A. The best answer is B.
C. 48 m/sec
D. 56 m/sec
23. At what initial velocity is the braking distance of the test vehicle equal to 100 meters, if the acceleration is -10 m/s2?
A. 38 m/sec
B. 44 m/sec
B is the best answer. Braking distance = Stopping distance Reaction distance. With a braking deceleration of 10 meters per second squared, the stopping distance at 40 meters per second is 110.0 meters, and the reaction distance is 30.0 meters (calculated from 40 m/s x 0.75 s), so the braking distance is 80.0 meters. At a velocity of 45 meters per second, the stopping distance is 135.0 meters, while the reaction distance is 33.75 meters, and the braking distance is therefore 101.25 meters. This means that for a braking distance of 100 meters, the velocity must be just less than 45.0 meters per second, making choice B the best answer. A very easy mistake to make is to read only the chart of stopping distances, and not to note that the question was asking about braking distance. This would have led you down a path of error, so that you would mistakenly choose A. The best answer is B.
C. 48 m/sec
D. 56 m/sec
