Interesting riddle/puzzle

[Tibbz2]

Edit it in.

 

Probably will this evening!

 

What actually happens depends on loss of factors and we haven't been given enough information to model the situation fully. .

There is all the information we need, to make a correct prediction.

Just think as if you've set it up yourself, the diameters are the same, both balls and strings have mass etc.

[Guest ecopley]

I think the reasoning still holds (apart from the predictive text/whisky errors). The strings would have to be very heavy to overbalance the buoyancy of the steel ball, which is where the puzzle is at.

Do feel free to correct me, though. It's only my tiny brain trying to puzzle it out.

I thought at first that the left side would fall but I hadn't taken the buoyancy of the steel into account.

Whatever the actual outcome it's certainly an interesting puzzle.

Any thoughts on the budgies?

[Guest peepshow]

. The ping-pong ball just represents empty space and exerts no force (it doesn't pull up - or at least the resultant force is zero because any upward force is balanced by downward force or it would be moving, which it can't).

 

 

Is that right?

Surely, there can be upward force without movement.  

 

A helium baloon on a string tied to the ground exerts an upward force via the string but there isn't any movement.

 

The ping pong ball is trying to rise and as it's prevented from doing this it is excerting a pull on the string. 

 

So I reckon that the left would rise due to this.

Edited March 18, 2014 by peepshow

[Guest ecopley]

That's a very attractive thought but if you compare that situation to standing in a boat and blowing on the sail you can see that the resultant force is zero. The ping-pong ball is pulling up but against what? If you weighed the components separately (ping-pong ball, string and beaker of water) they would with the same as they would of you assembled them as per the diagram. The steel ball is supported from outside the beaker. If you weighed the ball on its stand and then put the beaker of water under it so the ball was submerged, the measured weight would change because, even though the ball sinks, the water bears weight equal to the displaced mass of water. The displaced mass is less than the steel so it will sink but it still has some buoyancy. If you did the same with beakers full of mercury, the steel would float and the string would be slack so it would be more obvious but the effect is present even in water.