A demonstration of the conservation of angular momentum using a Hoberman sphere. Angular momentum depends on the rotational velocity of an object, and on its rotational inertia. When an object changes its shape, its angular velocity will also change.pic.twitter.com/UUQqALp3HW
The only thing I quibble with in this animation is that there is energy transferred to the spinning when he pulls the string, making the effect look more exaggerated.
-
-
Is there, though... His energy is constrained to the vertical, doesn't look like it can transfer to rotational
-
yes .. it's applying an external torque along the rotation axis .. i.e. it's not a closed system
- 11 more replies
New conversation -
-
-
That IS the effect isn’t it: Smaller radius, faster rotation, and vice versa...right?
-
yes it is the effect but the relation is only so simple when there is no external torque (see my reply to my previous tweet)
End of conversation
New conversation -
-
- 1 more reply
New conversation -
-
It's not exaggerated, the system would gain the exact same amount of kinetic energy if it pulled itself in.
-
I don't think so .. kinetic energy goes as L_1^2/2I_1 +mgΔh so the fact that the CM is lifted under gravity means work is done and that must be accounted for in the rotational motion
- 3 more replies
New conversation -
-
-
I’m going to make some actual measurements and update .. but my original back of the envelope estimated that the rotational velocity at the top was too high
- 1 more reply
New conversation -
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.