Posted by Anonymous on .
A large grinding wheel in the shape of a solid cylinder of radius 0.450m is free to rotate on a frictionless, vertical axle. A constant tangential force of 180 N applied to its edge causes the wheel to have an angular acceleration of 0.870 rad/s2. (a) What is the moment of inertia of the wheel? (b) What is the mass of the wheel? (c) If the wheel starts from rest, what is its angular velocity after 8.00 s have elapsed, assuming the force is acting during that time?

Physics Elena please help! 
Elena,
Nnewton’s 2 Law for rotation
M = I•ε,
where angular acceleration ε=0.87 rad/s²,
the torque M = F•R ,
the moment of inertia I=mR²/2 ,
F•R= m•R²•ε/2,
m=2•F/R•ε=2•180/0.45•0.87=919.54 kg
I=mR²/2=919.54•0.45²/2=93.1 kg•m².
ω= ε•t=0.87•8=6.96 rad/s