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?