Calculating Rotational Speed Change When Adding Mass to a Rotating Object"

[rdmachinist]

If a rotating 40 lb. mass has a non rotating 1 lb. mass instantly added to it's central axis, how much will the rotating mass slow down? Secondly, all else equal, does the rotational speed change the proportionality with which the smaller mass slows the larger (inverse square or some such law)?

 

[DrGreg]

If a rotating 40 lb. mass has a non rotating 1 lb. mass instantly added to it's central axis, how much will the rotating mass slow down? Secondly, all else equal, does the rotational speed change the proportionality with which the smaller mass slows the larger (inverse square or some such law)?

There's not enough information to answer the question: it depends on the shapes of the masses. Assuming a vertical axis:

• If the large mass was tall and thin, and the small mass was short and fat, the large mass would slow down a lot.
• If the large mass was short and fat, and the small mass was tall and thin, the large mass wouldn't slow very much.

Do you know about angular momentum? Or moment of inertia?

 

[rdmachinist]

I'll look into these terms more thoroughly and repost at a later date if nessesary. Thanks for the reply.