Principle and Working:
Coplanar forces (weight, spring balance) act on the moments disc on either side of the pivot. In equilibrium, the moments are determined as a function of the magnitude and direction of the forces and of the reference point.
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The spring balance is adjusted to zero in the position in which the measurement is to be made in each case. The straight line from the push-in button to the pivot point is adjusted to the horizontal by moving the swivel clamp on the stand rod. The fishing line to weight pan then runs along a row of holes. The spring balance should be mounted in the swivel clamp so that it forms an angle with the fishing line.