Theory:

Levitation:
A process in which an object floats on the air without any support is known as levitation.
When two bar magnets are placed so that the like (similar) poles are placed on the same side, the object will levitate.
 
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Levitation of bar magnets
 
Since the like poles of the magnet repel each other, by the property of repulsion, a magnetic object can levitate.
A levitating propeller:
This activity requires ring magnets, two \(500\ ml\) plastic bottles, sand, and a plastic straw.
 
1. A \(500\ ml\) plastic bottle is cut in the shape of a propeller as shown in the figure. Also, a hole is made in its bottle lid.
 
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Top of a plastic bottle and its cap
  
2. Another plastic bottle half-filled with sand is taken and closed with the lid having a hole. A plastic straw is inserted through the lid into the bottle and placed erect.
 
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A sand-filled plastic bottle with a straw
 
3. Two ring magnets are placed on the bottle propeller, one inside and the other outside the lid. These magnets will attract each other and stick tightly.
 
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A cap and the ring magnets placed on the top of the bottle
 
4. Another ring magnet is placed through the straw, and the propeller with the magnets are placed on the straw.
 
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Ring magnets inserted on the straw
 
5. The magnets, placed in the straw, and the propeller are positioned to repel each other so that the propeller levitates. We can keep this setup under a ceiling fan to make the propeller spin faster.
 
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A home-made propeller
 
The repulsion property of a magnet levitates the bottle fan.