# Conservation of Angular Momentum Problem Help

• yus310
In summary, a small bob of putty with mass m falls from the ceiling onto the outer rim of a turntable with radius R and moment of inertia I_0. The turntable is rotating freely with angular speed w_i about its vertical fixed symmetry axis. After several turns, the putty flies off the edge of the turntable. The question asks for the final angular speed of the turntable after the putty flies off. Using the conservation of angular momentum, we can set the initial angular momentum equal to the final angular momentum and solve for w_f. A follow-up question asks if the final angular velocities of the turntable and putty are different or similar, and if the answer is logical. Another question refers to a link

## Homework Statement

Ok... "A small bob of putty of mass m falls from the ceiling and lands on the outer rim of a turntable of radius R and moment of inertia I_0 that is rotating freely with angular speed of w_i, about its vertical fixed symmetry axis..."

"After several turns the blob flies off the edge of the turntable. What is the angular speed of the turntable after the blob flies off."

## The Attempt at a Solution

Ok.. so angular momentum is conserved... so when the blob hits the turn table

..
I_0*w_i=(I_0+m*R^2)w_f

Solve for w_f...

but when the blob flies off, do they does the final angular velocities of the turntable and putty different or similar? Does the putty fly off with a velocity of w_f or something else... does this look logical?

Angular Momentum Initial= Angular Momentum Final...
But what next?

Go to...

http://www.nd.edu/~agoussio/10310_spring2006/2006_exam3.pdf [Broken]

MC5

... Wouldn't the answer be that w_0=w_f... because when you put two things in the opposite direction, that means they'll be moving at the same velocity... is this right? Or it is that they'll move slower and w_0>w_f...

.5*m*w_0*(3R^2)=.5*m*w_f*(R^2)?

Wrong or Right? Thanks.

Last edited by a moderator: