Question

A 40 kg boy sits 1.2 m from the fulcrum of a see-saw. Where should another boy of 30 kg sit on the other side in order to balance it ?

Answer 1

Explanation:

For a lever,

Load x Load arm = Effort x Effort arm

Here, take the 50 kg boy as the load and the 40 kg boy as the effort.

50 x 1.2 = 40 x effort arm

60 = 40 x effort arm

Effort arm = 1.5 m

So if the 50 kg boy sits 1.2 m from the fulcrum of a see-saw then the other boy of 40 kg should sit on the other side at a distance of 1.5 m from the fulcrum.

Answer 2

Answer:

• 1.6 m.

Explanation:

Given:

• Load = 50 Kg
• Load arm = 1.2 m
• Effort = 30 Kg

To find:

• Effort arm

Solution:

From the principle of moments:

> Load × Load arm = Effort × Effort arm

=> 40 × 1.2 = 30 × x

=> 48 = 30x

=> x = 48/30

∴ x = 1.6 m

• Hence, the boy should sit at a distance of 1.6m on the other side to balance the see-saw.