A 89.1-kg horizontal circular platform rotates freely with no friction about its
ID: 1731205 • Letter: A
Question
A 89.1-kg horizontal circular platform rotates freely with no friction about its center at an initial angular velocity of 1.75 rad/s. A monkey drops a 9.37-kg bunch of bananas vertically onto the platform. They hit the platform at 4/5 of its radius from the center, adhere to it there, and continue to rotate with it. Then the monkey, with a mass of 20.3 kg, drops vertically to the edge of the platform, grasps it, and continues to rotate with the platform. Find the angular velocity of the platform with its load. Model the platform as a disk of radius 1.71 m.
Sapling Learning macmillan learning A 89.1-kg horizontal circular platform rotates freely with no friction about its center at an initial angular velocity of 1.75 rad/s. A monkey drops a 9.37-kg bunch of bananas vertically onto the platform. They hit the platform at 4/5 of its radius from the center, adhere to it there, and continue to rotate with it. Then the monkey, with a mass of 20.3 kg, drops vertically to the edge of the platform, grasps it, and continues to rotate with the platform. Find the angular velocity of the platform with its load. Model the platform as a disk of radius 1.71 m Number 0.868 rad/sExplanation / Answer
New moment of inertia i2 = inertia of platform + bananas +monkey
= m1r^2/2 + m2*(4r/5)^2 + m3*r^2
= 89.1*1.71^2/2 + 9.37*(4*1.71/5)^2 + 20.3*1.71^2
= 207.16
initial i1 = m1r^2/2= 89.1*1.71^2/2 = 130.27
By angular momentum conservation , i2w2 = i1w1
w2 = i1w1/i2
= 130.27*1.75/207.16
= 1.1 rad/s
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