Torque pulley homework help

  • #1

Homework Statement

Two blocks are connected by a string of negligible mass passing over a pulley of radius .25 m and moment of inertia I. Block 1 is on an incline of 37 degrees and block 2 is hanging down. The hanging mass is accelerating down at 2 m/s^2. Find I. (I already know tensions T1 and T2)

Homework Equations

Tnet = I*[tex]\alpha[/tex]

The Attempt at a Solution

T1(incline block) = 118 N, T2(hanging block) = 156 N
.25*156-.25*118cos(37) = I(2/.25)

I think you need the cos(37) because T1 (on the incline) has a vertical component that does not contribute to the torque. Is that correct?
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  • #2
Otherwise, the answer I got was wrong.Any help is appreciated! Yes, the cos(37) factor is correct. The torque that the vertical component of T1 produces is equal to T1*cos(37). That's why you need to subtract it from the total torque (T2*r) in order to get the torque due to only the net force (Tnet).

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