A uniform meter stick balances on a fulcrum placed at the 40 cm mark when a weight W is placed at 30 cm mark. What is the weight of the meter stick? How to calculator it ?

2 answers

"Calculator" is a noun. I suspect you meant to wrote the verb "calculate".

To get the weight, set the moment about the fulcrum e
Whoops! My computer is sending off answers before they are done. The ruler weight W' acts at the 50 cm mark. Let W be the weight added at the 30 cm mark to produce balance.

Set the total moment about the fulcrum equal to zero.

W*10 - W'*10 = 0
W = W'

You need to know the force that produces balance, W, in order to compute the ruler weight, W'.