Ok so this question was posted before but I'm confused by the answer. The problem is: The two masses (m1 = 5.0 kg and m2 = 3.0 kg) in the Atwood's machine shown in Figure 10-23 are released from rest, with m1 at a height of 0.87 m above the floor. When m1 hits the ground its speed is 1.4 m/s. Assume that the pulley is a uniform disk with a radius of 12 cm. Find the mass of the pulley.

Question

Ok so this question was posted before but I'm confused by the answer. The problem is: The two masses (m1 = 5.0 kg and m2 = 3.0 kg) in the Atwood's machine shown in Figure 10-23 are released from rest, with m1 at a height of 0.87 m above the floor. When m1 hits the ground its speed is 1.4 m/s. Assume that the pulley is a uniform disk with a radius of 12 cm. Find the mass of the pulley. 
Since the pulley is a disk that means I = 1/2mr^2 and omega is vfinal/r. I have my equation 1/2(m2 + m1)vfinal^2 + 1/2Iw^2 = m1gh but I don't know what I'm doing wrong.

bobpursley · Answer

Solve for I in that equation, then from knowing the value of I, set it equal to 1/2 masspulley*radius^2 and solve for the masso of the pulley. radius pulley=.12m