A $55\mathrm{.}0kg$ grindstone is a solid disk $0\mathrm{.}530m$ in diameter.

You press an ax down on the rim with a normal force of

$F=180N($Figure $1).$ The coefficient of kinetic friction

between the blade and the stone is $0\mathrm{.}60,$ and there is a

constant friction torque of $6\mathrm{.}50N*m$ between the axle of

the stone and its bearings.

Part A

How much force must be applied tangentially at the end of a crank handle $0\mathrm{.}500m$ long to

bring the stone from rest to $120re\frac{v}{m}in$ in $9\mathrm{.}00s?$

After the grindstone attains an angular speed of $120re\frac{v}{m}in,$ what tangential force at the

end of the handle is needed to maintain a constant angular speed of $120re\frac{v}{m}in?$

Part C

How much time does it take the grindstone to come from $120re\frac{v}{m}in$ to rest if it is acted on

by the axle friction alone?

Express your answer with the appropriate units.

$t=$