Question

A car is moving at a speed of 72 km/hr. If the wheels of diameter 0.5 m are stopped in 20 rotations by
applying the brakes, angular retardation produced by the brake is :
5.5 rad/s2 (B) 33.5 rad/s2
(C) 29.5 rad/s2 (D) 25.5 rad/s2​

Answer 1

Answer:

Here: Speed of car = 72 km/hr =72×518=20cm/s

Diameter of each wheel=0.52m

Number of rotation = 20

The relation for angular speed is ω=υr=200.25=80 rad/sec

Angular displacement Q=2π×20=40 π rad

The relation for angular retardation is given by

ω2=ω20+2aQ 0=(80)2+2a(40π) Or a=(80)280π=−25.5rad/s2