Question

A car is moving on a straight road with uniform
speed of 10 ms-1. The driver notices a red signal
70 m ahead of him. He applies brake causing
retardation 1 ms? If reaction time is 1 s, then the
distance of car from red signal when it stops is
(1) 10 m
(2) 50 m
(3) 20 m
(4) 70 m​

Answer 1

Answer:

10 m

Explanation:

For 1 second reaction time distance travelled by car is

x = speed × time

= 10 m/s × 1 s

= 10 m

So, red signal is now only 60 m ahead

Stoping distance of car is

S = (v² - u²)/(2a)

= [(0 m/s)² - (10 m/s)²]/(2 × -1 m/s²)

= (100 m²/s²) / (2 m/s²)

= 50 m

Out of 60 m, car travels 50 m and finally stops. The resultant distance left between car and signal is then 10 m.