The movement of a fluid during convection is a circular/oval motion since the fluid at the top sinks and the fluid at the bottom rises.
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Answer:
Torque, 
Explanation:
It is given that,
Force acting on the particle, 
Position of the particle,
We need to find the torque on the particle about the origin. It is equal to the cross product of position and the force. Its formula is given by :
The cross product of vectors is given by :

or

So, the torque on the particle about the origin
. Hence, this is the required solution.