Figure shows a lamina in x-.y plane. Two axes z and z' pass perpendicular to its plane. A force F acts in the plane of lamina at point P as shown. Which of the following statements is incorrect? (The point P is closer to z'-axis than the z-axis).

detailed solution

Correct option is D

The direction of τ→ is given by right handed screw rule.According to this rule, the direction of τ→ caused by F→ about z axis is along k^.Hence, option (1) is correct.Again, according to this rule, the direction of τ→1 caused by F→ about z' axis is along -k^Hence, option (2) is also correct.As τ → = r→ ×F→ and P closer z'axis, therefore, τ→1 caused about z' axis is smaller than τ→ .Hence option (3) is also correct.It is meaningless to add torques about two different axes.Hence, option (4) is incorrect.