Question

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Q. On a see-saw, two children of masses 30kg and 50kg are sitting on one side of it at distances 2m and 2.5m respectively from its middle. Where should a woman of mass 74kg sit to balance it?
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Topic:– Force
Class:— X


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Answer 1

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Let the two children be sitting on the left arm. They will produce anti-clockwise moment due to their weights about the middle point. 

Total Anti-clockwise moment ,

= 30kgf × 2m + 50kgf × 2.5m 

= 60kgfm + 125kgfm

= 185kgfm 

To balance it, the man should sit on the right arm (to produce clockwise moment).

Let his distance from the middle be x m.

Then

Clockwise moment = 74kgf × xm

= 74xkgf m

By the Principle of moments,

Anti-clockwise moment = Clockwise

185 = 74x

x = 185/74m

= 2.5 m ( On the Other Side ).

• I Hope it's Helpful My Friend.

Answer 2

Hello Mate! Here is your answer:

Given,

Children Masses = 30 kg and 50 kg

Total mass on one side = (30+50) kg

= 80 kg

Mass of Woman = 74 kg

Let x be the distance of woman from the centre of see saw,

According to the Principle of Moments,

Sum of Clockwise Moments = Sum of Anti-Clockwise Moments

= (30*2) + (50*2.5) = (74*x)

= 60+125 = 74x

= 185 = 74x

= 2.5 m = x

The Woman must sit at 2.5 m from the centre.

I hope this helps.