A driver can stop his car from the red signal at a distance of 20m when he is driving at 36 kmph and 41.25m when he is driving at 54 kmph. 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 36 kmph and 41.25m when he is driving at 54 kmph. 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 equation `3.75=7.5t` `t=0.5s`