Question

A car is travelling with a speed of 72 kmph and its
acceleration (a) = 5 m/sec2. The reaction time of driver to
apply brakes is 1.5 seconds. calculate the total stopping
distance​

Answer 1

first of all we have

speed of the car=72km/hr

acceleration of the car=5m/sec²

reaction time=1.5sec

now we convert either the speed to m/sec or acceration to km/hr. For convinience we convert speed

speed of car=72×(5/18)m/sec

=20m/sec

now though the 3rd law of sir Issac Newton we have this

s=ut+1/2at²

s=20×1.5+(1×5×1.5×1.5)/2

s=30+5.625

s=35.625

so the distance covered after applying brakes is 35.625m