What is the Mass of the Ruler on a Sharp Edge?

[Miri]

Turning effects of forces 3

Homework Statement

A ruler of an unknown mass is 52.0cm long. To find out its mass, you put a stone of 100g on the ruler 3.0cm from its end and balance the ruler on a sharp edge. The ruler is balanced when the supporting edge is 15.0cm from its end. Calculate the mass of the ruler.

Homework Equations

I know that the force of the stone is 0.981N. But what do I have to do to find out the force pointing downward of the ruler, so that I can find the mass...?

 

[Hootenanny]

Homework Statement

A ruler of an unknown mass is 52.0cm long. To find out its mass, you put a stone of 100g on the ruler 3.0cm from its end and balance the ruler on a sharp edge. The ruler is balanced when the supporting edge is 15.0cm from its end. Calculate the mass of the ruler.

Homework Equations

I know that the force of the stone is 0.981N. But what do I have to do to find out the force pointing downward of the ruler, so that I can find the mass...?

This question is very similar to your other thread, turning forces 4 and can be tackled in a very similar manner.