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Attached on a 1 unit long and weightless cord are 2 identical balls w/ 1 unit mass.
If it slides on hook J w/out friction.. the high ball can be pulled horizontally to distance (d)
away from J so that when released it can hit the other ball. Can I assume that the low
ball is at rest on time of collision?

Is this homework?

 

 

Can I assume that the low
ball is at rest on time of collision?

 

How can it be?

 

Although this is a dynamic question so not an equilibrium one, you can resolve the forces acting on the balls.

Is the ball simply released with the system in a static position?

 

What force would be required to maintain the lower ball at rest prior to collision?

Edited March 22, 201510 yr by J.C.MacSwell

 

JCMacSwell

Is the ball simply released with the system in a static position?

 

What force would be required to maintain the lower ball at rest prior to collision?

 

 

That mkes no more sense (ie is incomplete) than the OP.

Edited March 22, 201510 yr by studiot

Can I assume that the low ball is at rest on time of collision?

 

Under the conditions you've given, yes.

I tried an experiment

 

swansont is correct, it will not move, so long as the masses are equal. +1

Edited March 22, 201510 yr by studiot

I tried an experiment

 

swansont is correct, it will not move, so long as the masses are equal. +1

thanks..

but the imagine the lower ball moving downward if there is a horizontal tug on the swinging ball.

Maybe your experiment has high friction..

I was directed to almost similar arrangement of this called Swinging Atwood Machine ( also known as smiles & tears).

Its a lot complicated than i thought. Below the red circles are pulleys.

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