Question

Figure 7.5 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 are true? (The point P is closer to z′-axis than the z-axis.)

(a) Torque τ caused by F about z axis is along cap -k  .

(b) Torque τ′ caused by F about z′ axis is along cap -k .

(c) Torque τ caused by F about z axis is greater in magnitude than that about z axis.

(d) Total torque is given be τ = τ + τ′.

Answer 1

(a) False, it is along cap k.

(b) True

(c) True

(d) False, there is no sense in adding torques about 2 different axes.