Answer to Question #118800 in Physics for Maria Maria

Question

Two children are playing on a seesaw. The light board has a length of 6.4m. The two playmates are already on
either end. Boy A has a mass of 40kg and the

Answer 1

Although the condition is incomplete, assume that boy A has a mass of 40 kg and sits at one end of the seesaw, while girl A has a mass of 30 kg and sits at the other end. Of course, the side of the boy will outweigh. Let us ask ourselves a question: To where should the boy move in order for the seesaw to be in equilibrium?

Solution

Apply torques equilibrium. For the seesaw to be in equilibrium, the torques on the boy's side must be the same as the torque on girl's side. The torque is force times lever:

$$T_B=T_G,\\ m_Bgd_b=m_Ggd_G,\\ \space\\ d_B=\frac{m_Gd_G}{m_B}=\frac{30\cdot3.2}{40}=2.4\text{ m}.$$

Therefore, the boy should move 80 cm closer to the center of the seesaw.