Understanding Magnetic Force and Weight in a Cylindrical Container

AI Thread Summary
In a cylindrical container, a magnet with weight W is placed on an analytical balance, while another magnet hangs above it, stationary. The top magnet experiences a downward weight and an upward magnetic force, while the bottom magnet feels its own weight and the magnetic force from above. The balance reading equals the combined forces acting on it, which includes both the weight of the bottom magnet and the magnetic force exerted downwards. Therefore, the reading on the balance is 2W, accounting for both the weight of the bottom magnet and the magnetic force acting on it. This illustrates the application of Newton's third law in the context of magnetic forces.
elitewarr
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Homework Statement


Placed in a cylindrical container of negligible mass, a magnet with weight W is placed on a analytical balance. Another magnet is placed on top of it, hanging in mid-air and is stationary. What is the reading of the analytical balance?


Homework Equations





The Attempt at a Solution


By drawing the free-body diagram, the magnet on top will have weight acting downwards and magnetic force upwards. The magnet below will experience weight downwards, normal reaction force up wards and magnetic force downwards. I know the magnetic force must = W since the magnet is not moving. However, why is the reading of the balance = W, and not >W?

Thanks.
 
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what do u mean by hanging in mid air? is it only balanced by the repulsive force against weight or it is hanging by some rope or anything?
 
It is only balanced by the repulsive force against weight.
 
elitewarr said:

Homework Statement


Placed in a cylindrical container of negligible mass, a magnet with weight W is placed on a analytical balance. Another magnet is placed on top of it, hanging in mid-air and is stationary. What is the reading of the analytical balance?

The Attempt at a Solution


By drawing the free-body diagram, the magnet on top will have weight acting downwards and magnetic force upwards. The magnet below will experience weight downwards, normal reaction force up wards and magnetic force downwards. I know the magnetic force must = W since the magnet is not moving. However, why is the reading of the balance = W, and not >W?

Thanks.
You're correct that the magnetic force is W. To answer the question, figure out the force that the balance exerts on the weight+cylinder -- that will be the reading of the balance.

Hint: your suspicion that the reading is >W is correct.
 
But, if I'm not wrong, there's Newton's third law. The magnetic force will also be exerted on the bottom magnet. So, there's the W of the magnet, and magnetic force W acting downwards as well. Doesn't this mean that total normal reaction exerted by balance will be 2W?
 
Yes, 2W is right.
 
Oh. Okay Thanks :D
 

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