A driver can stop his car from the red signal at a distance of 20m when he is driving at 36kmph and 41.25 m when he is driving at 54kmph. Find his reaction time.

A driver can stop his car from the red signal at a distance of 20m whe

1.	A driver can stop his car from the red signal at a distance of 20m when he is driving at 36kmph and 41.25 m when he is driving at 54kmph. Find his reaction time.
Answer» Solution :LET t is reaction time of driver during which he MOVES with uniform speed Distance covered during reaction time `=S_(1)=ut` As he applies BRAKES, distance covered before coming to rest is `S_2=u^2/(2a)` TOTAL distance covered is `S=ut+u^(2)/(2a)` `20=10t+(100)/(2a).....(1)` `41.25=15t+(225)/(2a)......(2)` Solving above EQUATIONS 3.75=7.5t t=0.5s