Question

a driver driving a truck at a constant speed of 20m/s suddenly saw a parked car ahead of him by 95m. He could apply brake after sometime to produce retardation of 2.5m/s.An accident was avoided. his reaction time is​

Answer 1

Answer:

The reaction time= 11.832 seconds

Explanation:

Let us first calculate the time needed for the truck to come to rest , that is final velocity v=0  intial velocity u=20m/s, retardation=2.5m/s²

time taken t

v=u- a×t

t= 20÷2.5

t=8s

s= u×t- (a×t²)÷2

95= 20t- 1.25t²

1.25t² -20t -95=0

t=19.8s, is the maximum time available to avoid the accident and the time needed to bring the vehicle to rest is 8s

therefore the reaction time of the driver = 19.8 - 8 =11.832 s