How Do You Calculate the Second Mass in a Static Equilibrium Problem?

[jfri14]

Homework Statement

A 0.105 kg meter stick is supported at its
40 cm mark by a string attached to the ceiling.
A 0.665 kg object hangs vertically from the
7.17 cm mark. A second mass is attached
at another mark to keep it horizontal and in
rotational and translational equilibrium.

If the tension in the string attached to the
ceiling is 21.2 N, find the value of the second
mass. Answer in units of kg.

Homework Equations

The acceleration of gravity is 9.8 m/s2
Sum of Forces= 0
Sum of Torques =0

The Attempt at a Solution

Since the sum of the forces =0
21.2N - 0.665kg*9.8m/s2 - x*9.8m/s2 = 0
1.47786 kg

I'm not sure why this isn't right or how to fix it

 

[Doc Al]

The Attempt at a Solution

Since the sum of the forces =0
21.2N - 0.665kg*9.8m/s2 - x*9.8m/s2 = 0
1.47786 kg

You left out the mass of the stick itself.

 

[jfri14]

Got it, thanks so much!