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Re: correct answer

On Thu, 9 Oct 1997, Martha Takats wrote:

Mark, if your answer is right, what happened to the other half of the
energy? Dissipative forces inside the uncoiling hose?

I think this must be the case. The force F = (dm/dt)v acting on each
element of mass dm over a distance dx = v*dt would give each element an
energy of (dm)v^2 and, therefore a velocity of v*sqrt(2) unless
dissipative forces came into play. In effect, each element gets jerked
into motion with an impulse greater than what is necessary to achieve the
final velocity. The excess work causes an increase in the internal

Thus, I think Mark is right and the book is wrong.

A. John Mallinckrodt
Professor of Physics
Physics Department voice:909-869-4054
Cal Poly Pomona fax:909-869-5090
Pomona, CA 91768-4031 office:Building 8, Room 223