POLL: Is Torque Important?

[DPelletier]

Its late and I had a thought. If you push a boulder up to the tippy top of a mountain. It takes a lot of energy to push that boulder to the top. Where did the energy go? Its still there as potential energy. When the boulder rolls back down the hill. It releases that energy as kinetic. When the boulder is back at the bottom the net result is 0 energy(stored?) It released all the energy. You spent the energy. Then it was undone. Not that no work was done. Just that the work was undone.



The change in the kinetic energy of an object is equal to the net work done on the object.



Its not that you didnt exert energy to do work. Its that the end result is no potential energy is stored.

Correct, it's known as the Law of Conservation of Energy.

I was trying to avoid getting drawn into Physics and Kinematics, but from my perspective, the cat analogy in the textbook that Ryan provided doesn't work well because they tried to simplify the example to make a point without recognizing the complex physics involved.

If you didn't need to accelerate to cross the room (somehow managed to simply be in motion at a constant speed) and you did it with no friction (like using a magnetic field) and you did it in a vacuum, then you would do no work moving the cat across the room. In reality, a human being walking is a very complex physics equation. As far as the "negative work" done by lowering the cat to the ground, I would say that if you let go of the cat, gravity is the force (@ 9. 81 m/s2) that returns that cat to earth and the human has done no work in that act.

On the other hand, its been a long time since I had to think about any of this so if someone thinks I'm wrong, please don't send a hit squad!



Cheers,

Dave

 

[NIsaacs]

Remember the commercial of the Dodge Cummins powered pickup, drag racing the Hemi powered dragster. All that HP, and he still lost to the mighty torque of the pickup. In fact all that HP went up in tire smoke, is that "negative work" I think the Cummins coulda pulled that parachute





"NICK"



PS, "OPPS", maybe it was a Hemi powered pickup, I forget.