Simple pulley question- single fixed

[gloo]

for a single fixed pulley system :

1. on both sides -equal length ropes
2. equal masses to balance each other (static)
3. ignoring weight of the ropes and friction (pulley, rope, air etc..)

..if no friction- can it be assumed that the next incremental bit of weight on either side- (say a big fly lands on one side of the mass) will tip the scale so that one side completely pulls down the other

 

[Andrew Mason]

for a single fixed pulley system :

1. on both sides -equal length ropes
2. equal masses to balance each other (static)
3. ignoring weight of the ropes and friction (pulley, rope, air etc..)

..if no friction- can it be assumed that the next incremental bit of weight on either side- (say a big fly lands on one side of the mass) will tip the scale so that one side completely pulls down the other

You don't have to assume it. You can work it out. If the weights are not equal, there is a net force so there will be non-zero acceleration: F=(m1-m2)g = m1a. If there is non-zero acceleration, the distance that the system will move in time t is s = at^2/2 so one side will completely fall eventually.

It should not be surprising that a fly would cause one side to fall. The real difficulty in practice would be to set up a frictionless pulley with equal masses on both sides so that they were exactly balanced.

AM