Question

3. On a see-saw, two children of masses 30 kg and
60 kg are sitting on one side of it at distances 2 m and
2.5 m respectively from the centre of the see saw. Find
the distance at which a man of mass 75 kg should sit
on the other side to balance the see saw​

Answer 1

Answer:

Explanation:

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 = 30 kgf x 2m + 50kgf x 2.5 m

= 60 kgf m + 125 kgf m = 185 kgf m

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 = 74 kgf x X m = 74x kgf m  

By the principle of moments,

Anti-clockwise moment = Clockwise moment

185 = 74x

or x = 185/74m

= 2.5 m (on the other side).