your doctor's scale has arms on which weights slide to counter your weight. these weights are much lighter than you are. explain how this works.

does this relate to stress/strain?

No. This is called a balance, and it operates on the principle of a lever in equilibrium.

The doctor's scale works on the principle of balancing forces. The arms of the scale have lighter weights that can slide along them, and these weights are used to counterbalance your weight.

When you stand on the scale, your weight exerts a downward force on the scale. To maintain equilibrium, an equal and opposite force must be applied to counterbalance your weight. The lighter weights on the scale's arms are used for this purpose.

The doctor starts by positioning the weights on the arms closer to the center of the scale. As these weights are much lighter than you, they exert a smaller force, resulting in an upward force. The doctor then gradually moves the weights outward along the arms until the upward force they exert perfectly balances your downward force. At this point, the scale remains level, indicating that the forces are balanced, and the doctor can read your weight.

Regarding the relation to stress and strain, stress and strain are terms commonly associated with the deformation of materials under applied forces. In this case, the scale is designed to measure your weight and not to undergo significant deformation. Therefore, the concept of stress/strain is not directly relevant to the functioning of the doctor's scale.