- #1

- 1,650

- 246

A piano rests on a frictionless surface. I am standing next to the piano (on a frictional surface) and I claim that the following two statements prove it is impossible for me to move the piano:

(1) ... The kinetic energy of the piano is equal to the work I've done on it.

(2) ... I can't do work on the piano unless it is moving. (But, because of (1), I can't get it moving unless I do work on it. But I can't do work on it unless it is moving... ad infinitum)

"Therefore the piano is immovable," I claim.

(1) is equivalent to the work-kinetic-energy theorem [itex]W=\Delta E[/itex]

(2) is a special case (where [itex]\frac{d\vec s}{dt}=0[/itex]) of the definition of work [itex]dW=\vec F\cdot d\vec s=\vec F\cdot \frac{d\vec s}{dt}dt[/itex]

Please explain where and why my logic is flawed (assuming I don't know Newton's laws).