8 March 2010 at 10:14 #28169
29 September 2012 at 20:35 #28175
Apologies for resurrecting an old topic but I was just directed here so am reading it (eep !) for the first time. I love these ideas but I have a question about number15:
“15.A 1 kg mass(or similar , tin of beans etcis probably better) is connected to some thick string and the rope wrapped around a wooden cylinder (rolling pin, or even a wine bottle will do as substitute).
When the rod is lifted what will happen?
(This can be done as a tie break, how many turns are needed for the tin to be lifted)
( the kilogram mass is held by the rope which doesn’t slip with a few turns)”
… I just can’t figure out what this is supposed to be doing. .. again sorry for resurrecting this for a silly question!
29 September 2012 at 23:41 #28176
The thick string is tied to the weight ( can of beans)
The free end of the string is then wound around the rolling pin and the end left loose.
When you lift the rolling pin as long as the string stays in contact with the rolling pin for a couple of turns then the can will be lifted.
Its like a ships windlass.or capstan.
[There is enough friction between the rolling pin and the string to support the weight of the can. A larger weight can be supported too as the increased tension in the rope increases the friction too.]
1 October 2012 at 09:37 #28177
A very similar effect to this Marvin and Milo “key drop” activity: http://www.physics.org/marvinandmilo.asp?id=47 .
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