Question

A uniform plank of a see saw 10m long is supported at its centre. A boy weighing 50kgf sits at a distance of 2m from the fulcrum. Where must a girl weighing 25 kgf sit so as to balance the plank?​

Answer 1

Explanation:

A boy is sitting at a distance of 1.5 m from one end.

Plank of see-saw is 5 m long.

The fulcrum of the see saw will be exactly at centre of plank i.e. 2.5 m

Thus, load arm is 2.5 - 1.5 = 1n

Thus,

Load arm x load = effort arm x effort

1 * 40 = EA * 25

Thus,

EA = 1.6m

Thus, the distance at which a girl must sit from other end is = 2.5 - Effort arm = 2.5-1.6 = 0.9 m