Question

Define the moment of force about an asix or a point when is it taken as positive

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Answer 1

Answer:

Explanation:

If the rotation of point B about O is considered, then the angular acceleration about that point O ,

Ω ~ (Fsinθ)r

=> kΩ = (Fsinθ)r

Where (Fsinθ)r = τ

Where τ is the torque of F about 0

Now τ = (Fsinθ)r = kΩ

τ j = kΩj

Which implies if you increase torque about j then Ω increases in the same direction.

Conventionally,

If 180° > θ > 0° then body rotates anticlockwise (see fig) and otherwise it rotates clockwise. Employing signs to anticlockwise direction as positive axis and clock wise direction as negative axis,

τ j = kΩj = r × F