Question

A seesaw is 4m long with a pivot at its midpoint.A boy who weighs 400 N sits at a distance of 1.5 m from the pivot. His sister weighs 300N.Calculate the distance at which the girl must sit if the beam is to be balanced
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Answer 1

Answer:

400 x 1.5 / 300

needs to sit at a 2m distance from the pivot i.e at the very end of the seesaw.

Answer 2

Answer:

The distance at which the girl must sit from pivot if the beam is to be balanced is 2 m

Explanation:

This is a case of rotational motion or we can say lever mechanism of torque balance

Length of seesaw = 4m

Weight of Boy$(W_{1})$ = 400 N

Distance of boy from pivot($d)$ = 1.5 m

weight of sister($(W_{2} )$  = 300 N

let 'x' be the distance of sister from pivot where she sit which result in balancing of  seesaw

For rotational equilibrium

$W_{2} *x =W_{1} *d$

300*x= 400*1.5

x = $4*1.5/3$

x = 2 m