A wheel free to rotate about its axis that is not frictionless is initially at r

Question

A wheel free to rotate about its axis that is not frictionless is initially at rest. A constant external torque of +59 N·m is applied to the wheel for 16 s, giving the wheel an angular velocity of +690 rev/min. The external torque is then removed, and the wheel comes to rest 120 s later. (Include the sign in your answers.) (a) Find the moment of inertia of the wheel. 15.089 Incorrect: Your answer is incorrect. kg·m2 (b) Find the frictional torque, which is assumed to be constant. 6.894 Incorrect: Your answer is incorrect. N·m

Explanation / Answer

Moment of inertia:

Wf=Wi+At

2pi*690/60= 0+A(16)

A=4.52 rad/seg^2

I=torque/A = 59/4.52=13.06kgm^2

For the frictional torque:

t1=120s

2pi*690/60= 0+A1(120)

A1=-72.26/120=0.602rad/seg^2

torque=I*A1=13.06kgm^2*0.602rad/seg^2=7.86s

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