Question

Question 25:
A bus running at a speed of 18 km/h is stopped in 2.5 seconds by applying brakes. Calculate the retardation produced.

Lakhmir Singh Physics Class 9

Answer 1

first we need to convert the given speed into si units=18km/h x 5/18
=5m/s.
given time = 2.5s
initial velocity=5m/s
final velocity=0m/s
retardation=(v-u)/t
=(0-5)/2.5
=-5/2.5
= -2m/s
here '-' sign represents the acceleration is produced in opposite direction
so in case of retardation we can ignore the sign