Intro to Moment of Inertia Video Lessons

Concept

Problem: A 2.2 kg, 20-cm-diameter turntable rotates at 80 rpm on frictionless bearings. Two 600 g blocks fall from above, hit the turntable simultaneously at opposite ends of a diagonal, and stick. What is the turntable's angular velocity, in rpm, just after this event?

FREE Expert Solution

From the conservation of angular momentum, the momentum before the event is equal to the momentum after the event.

$\overline{){{\mathbf{I}}}_{{\mathbf{i}}}{{\mathbf{\omega }}}_{{\mathbf{i}}}{\mathbf{=}}{{\mathbf{I}}}_{{\mathbf{f}}}{{\mathbf{\omega }}}_{{\mathbf{f}}}}$

The initial moment of inertia,

Ii = (1/2)Mr2

Radius, r = 20/2 = 10 cm

Ii = (1/2)(2.2)(10 × 10-2)2 = 0.011 kg•m2

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Problem Details

A 2.2 kg, 20-cm-diameter turntable rotates at 80 rpm on frictionless bearings. Two 600 g blocks fall from above, hit the turntable simultaneously at opposite ends of a diagonal, and stick. What is the turntable's angular velocity, in rpm, just after this event?