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On Oct. 9, Mark Shapiro wrote:
answer
In preparing for class today I was reviewing some problems in
Halliday, Resnick and Walker (5th ed) - Chapter 7. I believe the
to problem 15E on page 150 is incorrect.the
The problem states that a 12 m long firehose is uncoiled by
pulling the nozzle end horizontally along a frictionless surface at
steady speed of 2.3 m/s. The mass/length of the hose is 0.25kg/m.How
much work has been done on the hose by the applied force when theentire
hose is moving?
An interesting comment on this. In the fourth edition, the problem
is on p. 184 (problem 27E). Everything is much the same except the
statement of the problem to be solved: "How much kinetic energy is
imparted in uncoiling 12 m of hose?"
This makes the problem easier, and the answer is certainly correct in
this case (with the obvious reasonable assumptions).