Question

A heavy boy and a lightweight girl are balanced on a massless seesaw. The boy moves backward, increasing his distance from the pivot point. What happens to the seesaw? a.It is impossible to predict without knowing additional information. b. The side the boy is sitting on will tilt downward. c. The side the girl is sitting on will tilt downward.d. Nothing; the seesaw will remain balanced.

Answer 1

Answer:

b. The side the boy is sitting on will tilt downward

Explanation:

Initially, the seesaw is balanced because the torque exerted by the boy is equal to the torque exerted by the girl:

$\tau_b = \tau_g\\W_b d_b = W_g d_g$

where

Wb is the weight of the boy

db is the distance of the boy from the pivot

Wg is the weight of the girl

dg is the distance of the girl from the pivot

When the boy moves backward, the distance of the boy from the pivot ($(d_b)$ increases, therefore the torques are no longer balanced: the torque exerted by the boy will be larger, and therefore the side of the boy will tilt downward.