A see-saw board is supported at its center by a fulcrum A 25 kg person sits 80 c

Question

A see-saw board is supported at its center by a fulcrum A 25 kg person sits 80 cm from center. A 15 kg person is sitting on the other side at the correct distance from the center so boar is horizontal and in static equilibrium Ignore weight of board
How far from center is the 15 kg person
How much force does the fulcrum exert on board
Suppose board is 2.4 m long and two people 25 kg and 15 kg are sitting on opposite ends of board. How far from 25 kg person should fulcrum be placed so that board could balance horizontally again. Ignore weight of board

Explanation / Answer

For equilibrium, 25*80 = 15*x

This gives x = 133.33 cm. So, 15 kg person should sit 133.33 mm away from the centre.

Force by fulcrum on board = 25 kg + 15 kg = 40 kg. (or 40*9.8 = 392 N)

For balance of 2.4 m long board, 25*x = 15(2.4-x)

This gives x = 0.9 m.

Hence, for balance of 2.4 m long board, the fulcrum should be placed 0.9 m from the 25 kg person.

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