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Nikhil_RG

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Nikhil_RG

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malawi_glenn

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According to whom?Angular Momentum and Torque are defined about a point. But Moment of Inertia of a body is defined about an axis.

Wikipedia:

Torque is defined as the product of the magnitude of the force and the perpendicular distance of the line of action of a force from the axis of rotation.

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Nikhil_RG

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My question comes from the fact that the basic expression to calculate angular momentum involves finding the cross product of the position vector of the particle and it's linear momentum. So there has to be a point about which the position vector is defined and the angular momentum would be calculated about that particular point.

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Nikhil_RG

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And in the case where the body is free to rotate in any axis and a force is acting at some point on it, which causes a Torque, which axis do we consider, since there are no limitations.

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Well, first of all, do you understand tensors?Orodruin , is there a textbook or resource that I could refer to to understand about Moment of Inertia Tensor.

You do not consider an axis. You consider the general equations of motion. There are some simplified cases such as an object rotating freely around a fixed point an object not subject to any net force (just torques).And in the case where the body is free to rotate in any axis and a force is acting at some point on it, which causes a Torque, which axis do we consider, since there are no limitations.

In the case where you fix the rotational axis, only the torque in the axis’ direction is relevant. This component will not depend on which reference point you pick as long as you pick a point on the axis.So there has to be a point about which the position vector is defined and the angular momentum would be calculated about that particular point.

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