Question

11U
.
12. When a boy weighing 20 kgf sits at one end of a 4 m
long see-saw, it gets depressed at this end. How can it
be brought to the horizontal position by a man
weighing 40 kgf.
Ans. If the man sits at a distance 1 m from the centre
on the side opposite to the boy.
​

Answer 1

By Principe of equilibrium or moment,

>>Moment in anticlockwise direction=Moment in clockwise direction

Note : See-saw length is 4 m

Means it would be pivoted at 2m at centre

If he sits at end the he is 2m from centre.

>>20*2=40*l

>>l=1 m