Meter Stick Mass Blog

The above image includes the pictures for step 1 parts A, B, and C.
A. The equations that we used for our initial plan are as follows:
Torque= Force x Lever Arm
Torque Clockwise = Torque Counter-Clockwise (when balanced)
W=mg
Our initial plan was to multiply the mass of the added weight by 9.8 to give us the total weight added to the ruler. We would then find the torque on the side of the weight (we'll use counter-clockwise torque to describe this) by multiplying the added weight by the distance from the pivot point (Lever arm, 30cm).
Since the center of mass of the meter stick itself wasn't changed by adding weight, its center of mass remained at 50 cm. We then found the distance to the pivot point from 50cm and found that it was 20cm for the clockwise lever arm. We did not know the weight of the meter stick, so we plugged in x for that.
The Clockwise torque = the Counter-Clockwise torque when balanced, so we set the two equations of (0.98N)(30cm)= (X)(20cm).
We would then solve for the weight and convert the weight to mass by dividing it by 9.8.

The above image includes all the work that I did in step 3 describing our procedure.
B. Our initial plan worked.
Balancing point was at 70cm, the lever arm of the weighted side was 30cm, the added weight was 0.1 kg, which weighs .98 N. The center of mass of the meter stick was at 50cm. the lever arm from the center of mass of the stick to the pivot point was 20cm. Our final mass of the meter stick was 150g.
C.
For the measurements we took see part B.
Our initial plan worked to solve the problem. When things are balanced the Counter-Clockwise torque will equal the Clockwise torque. The center of mass of the meter stick was unchanged throughout the whole lab. We remembered that when we found the weight of the meter stick we needed to convert it to mass by dividing it by 9.8. The actual mass of the meter stick was only 0.8 off of what we had calculated.
D.