Question

A flywheel is rotating at 180 rpm and after 20s it is running at 120rpm. If the retardation is uniform, a) how many revolution will it make? B) what time will be elapsed before it stops

Answer 1

inital rounds in one second (u)=3=6πradian/sec

final rounds in one second (V)=2=4πradian/sec

time it take=20 second

since the motion is uniform

we can use,the first law of uniformlu accelerated motion

V=u+at

4=6+20a

a=-2rad/sec^2

time in which it elasped

in that case

V=0

a=-2

U=6

0=6-2t

t=3sec