Welcome to the PF.I need help with this attached question! The answer is supposedly B because of something to do with lever arms. But I don't get it at all!
The first drawing shows the bow in the drawn position ready for firing. In that position the pulley is stationary.Why isn't the pulley moving?
Hint: What do levers do? If B moves a short distance does A move the same distance? More? Less? Same speed as B? Faster? Slower?Why isn't the pivot in the middle?
A pulley can be thought of as a lever, at any given instant. A centrally mounted pulley isn't a very interesting lever because it's 1:1; the distance from fulcrum to contact point is the same for both ends of the contact. If the pulley is eccentrically mounted (and sufficiently frictional that the string does not slide) then it will behave like a lever, except that as the pulley turns the lever ratio will change.How do you determine that this is a lever question instead of a pulley question? I don't really understand how this system acts as a system of levers.
No. The pivot point is the dot, yes? In position 1, string B extent is closer to the dot where it reaches the pulley than is string extent A.Isn't B farther away from the pivot point than A in position 1?
Bottom pulley is the same, by symmetry. Only the pulleys separating extent A from extent B are relevant.Why are we ignoring everything but the top pulley.
Levers also change velocities. If B moves slowly what happes to A ?Q2) Forces farther away are less than when they are close.