rotational motion question is below

Question

A 1-kg rock is suspended from the tip of a meter stick at the 0-cm mark so that the meter stick balances like a seesaw when the fulcrum is at the 25-cm mark. From this information, what is the mass of the meter stick?

Answer 1

well if the mass is m, we have two forces acting downwards.

A force of 1g = g N downwards at the 0 cm mark, and a force of mg acting downwards through the centre of gravity of the stick which is halfway along the stick at the 50 cm mark.

As the stick is balance the two forces multiplied by the distance from the fulcrum must be the same

So g x 0.25 = mg x 0.25 so m = 1 kg