Originally Posted by
woodcraft
OK try this:
Spin your arms in a cranking motion for one minute,
then do it again with three lb. dumbbells.
Notice any difference?
I just did this.
Without the weights, it was not too hard.
with the weights, my arms got quite tired, & my breathing was starting to elevate. I would probably have reached failure within a second minute.
Conclusion: weight DOES matter.
YMMV
Were the weights you were spinning in free air or attached to a crank? If they were in free air they weren't balanced and it takes work to move them up and down.
Here's a thought experiment for you: Elevators are typically designed with a counterweight system. The counterweight is sized to equal the weight of the elevator plus a portion of the load but for this experiment assume the counterweight exactly balances the elevator. To move the elevator up an down in this scenario the motor only needs to overcome friction because the system is balanced. Add and equal weight to the elevator and the counterweight and the system remains in balance and it doesn't take any more power to move the elevator at a steady speed.