we know that in rolling motion the top of drum has linear velocity 2v if the centre of mass has linear velocity v. thus if a board moves over a drum without slipping it wil roll 2vt=2L if the center of mass moves vt=L in time t, and this result is independent of size of the drum. but when i do this with a pen or pencil rolling by my hand i always find that the pen moves the distance equal to length of my hand. do it yourself and please comment on this.
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