1.

A bot of mass `30kg` starts running from rest along a circular path of radius `6m` with constant tangential acceleration of magnitude `2m//s^(2)`. After `2sec` from start he feels that his shoes started slipping on ground. The friction coefficient between his shoes and ground is `mu`. Find `2/(mu)`. (Take `g=10m//s^(2)`)

Answer» Correct Answer - 6
After `2` sec speed of boy will be
`v=2xx=4m//s`
At this moment centripetal force on boy is
`F_(r)=(mv^(2))/R=(30xx16)/6=80Nt`.
Tagential force on boy is
`F_(t)=ma=30xx2=60Nt`.
Total friction action on boy is
`F=sqrt(F_(t)^(2)+f_(t)^(2))=100Nt`
At the time of slipping
`F=mug`
or `100=muxx30xx10`
`=mu=1/3`


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