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*From*: Dan Crowe <dcrowe@SOTC.ORG>*Date*: Tue, 3 Feb 2004 17:08:16 -0600

The board is always in contact with the top of the drum.

If the drum rolls without slipping, then the velocity

of the top of the drum is twice the velocity of the

center of the drum. Therefore, the board moves twice

the distance covered by the center of the drum. Note

that the board is in contact with different points on

the circumference of the drum as the drum rolls.

Daniel Crowe

Oklahoma School of Science and Mathematics

Ardmore Regional Center

dcrowe@sotc.org

-----Original Message-----

From: Justin Parke [mailto:FIZIX29@AOL.COM]

Sent: Tuesday, February 03, 2004 11:03 AM

To: PHYS-L@lists.nau.edu

Subject: rolling

I need some help with the following question from Halliday et al (6th ed.),

ch. 12 question 5:

"A woman rolls a cylindrical drum, by means of a board on top, through the

distance L/2, which is half the board's length. The drum rolls smoothly, and

the board does not slide over the drum.

a) What length of board has rolled over the top of the drum?

b) How far has the woman walked?"

The answers in the book are L and 1.5 L. I am not sure I understand what is

meant by "what length of board has rolled over the top of the drum." It seems

to me that it should be L/2. If the questions means how far has the board

moved with respect to the ground then I agree it is L.

Answers in algebraic form (plus verbal explanations) are preferable to

strictly verbal arguments.

Justin

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