Question

A vehicle is travelling at 25.0 m/s. It brakes provide an acceleration of -3.75 m/s^2[forward]. What is the driver's maximum reaction time if she is to avoid hitting an obstacle 95.0 m away?
the answer is a number less than 0.5 second. can you tell me the exact number and can you show me how to solve it?

Answer 1

The BRAKING time to stop is
T = 25/3.75 = 6.667 s

The distance travelled while decelerating is:
Vaverage*T = (1/2)(25)*6.667 = 83.33 m

She can travel only 95-83.3 = 11.7 m before applying the brakes.

Her reaction time must be t = 11.7/25.0 = 0.47 seconds or less, since 11.7 m is the maximum distance she can travel, at 25 m/s, before braking.

Answer 2

physics is hard