A square lamina OABC of side 10 cm is pivoted at O. Forces act on the lamina as shown in the original figure. If the lamina remains stationary, the magnitude of F is:

Question

G1 Physics · Accepted Answer

Take moments about the pivot O, so the unknown reaction at O gives no torque. From the original figure, the vertical 10 N forces at A and B produce equal and opposite torques and cancel. The vertical force at C passes through O, so its torque is zero. The horizontal 10 N force at A also passes through the horizontal line through O, so its torque is zero. Only two horizontal forces contribute to the remaining torque balance: 10 N at B and F at C. Both have the same perpendicular distance 10 cm f…