A weightless and perfectly flexible rope is hung over a weightless, frictionless pulley attached to the roof of a building. At one end is a weight which exactly counterbalances a monkey at the other end.
What happens if the monkey begins to climb ?
Subscribe to:
Post Comments (Atom)
Posts
The monkey exerts a force F downward. So the total force on the weight is W+F upward and W downward. So the weight accelerates upward.
ReplyDeleteSuppose the monkey stays still or moves downward. Then the total angular momentum around the pulley is now conserved. So the monkey must accelerate upward.
I guess you can directly argue about this by only using Newton's third law: in the absence of an external force, the system keeps its velocity (in this case it is 0). Monkey is attached to the rope, so whatever force it exerts is internal force of the system, so it can't change its position.
ReplyDeletebut this doesn't match with the above answer of murali that initially both will go up... what am i missing?
ReplyDeleteI think the system keeps it's velocity right ? the box containing the system is not moving since there is no external force.
ReplyDelete