Stephen Meschke's practice log

Stephen Meschke#

balance, 60 minutes

Is it easier to balance a rod with weights at both ends, or weight in the middle?

I got the question from this thread: http://www.jugglingedge.com/smalltalk.php?ThreadID=2599

Here are my results so far: https://youtu.be/FpwzuLx0l_8

Edit:

The left side of the video shows balance of a carbon fiber arrow shaft with weights (40g each) at the top and the bottom.

The right side of the video shows balance of a shaft with a weight (80g) in the middle.

This is an inverted pendulum. Both configurations have equal mass, length, and center of mass. It is much easier to balance when the weights are placed at the top and the bottom of the shaft.

Total practice time: 60 minutes

Location: garage

Comments (8)
James Hennigan - A rod with a weight at both ends and a rod with a weight at the top are equally difficult to balance (assuming these weights have the same mass). This is because the weight at the pivot contributes nothing to the torque or the moment of inertia.
James Hennigan - A rod with a weight at the top is easier to balance than a rod with a weight in the middle. Since a rod with weights at both ends is equivalent to a rod with a weight at the top, the rod with weights at both ends should be easier to balance than a rod with a weight in the middle.
7b_wizard - I'm afraid, with a mass at both ends, the lower mass will take the mass center down to the middle of the rod; compared to a weight on top only, where the mass center will be near the top.
7b_wizard - And the mass center is imho what you're sustaining and balancing, .. if it's nearer to the top, thus farther away from pivot point, it'll be the easier variant, i think.
Stephen Meschke - On the right side, I should have placed the weights at the top. Experiments will continue.
Stephen Meschke - I have found that tactile feedback is an important component of balance. When all the mass is at the top there is very little tactile feedback, which make the balance more difficult.
7b_wizard - See also: https://de.wikipedia.org/wiki/Wikipedia:Auskunft#angewandte_Physik_-_mech._Gleichgewicht_--.3E_Balancieren - "as long a rod as possible and heavier towards top for slowly changing angle, as heavy as possible for slower inertial mass
7b_wizard - .. I still believe a long light part on top better and earlier indicates the changing angle.