Question

When the pivot point of a balance is not at the center of mass of the balance, how is the net torque on the balance calculated? When a force is applied directly to the pivot point of a balance, what is the torque due to that force?

Answer 1

Net torque is calculated by multiplying the force with distance from the point of application of force to the point of pivot .

If more than 2 forces are present, then we either subtract the product of forces with their respective distances from pivot point or we add them . It depends on whether they both are present on opposite sides of pivot or on same side of pivot .

When a force is applied directly to the pivot point of balance, then the torque on due that force = 0 (zero) .

It is so because the torque is defined as the product of force and perpendicular distance from the pivot point but here the distance is 0 , therefore torque is zero.