During class we where issued an assignment which was to find out the weight of a ruler without using a scale. We started by doing some demo experiment, one was to show an unbalanced torque and explain why.
This picture shows that the right side of the ruler is shorter, so it will have a smaller torque, they both have the same lever arm distance but the right side has a greater torque therefore has the greater toque and rotating the object clockwise.
In the last demo we where asked to add a 100g mass one side and still make it balance, so we just made the balance point closer to the weight so it could balance.
by looking at this picture we can see that the balancing point is closer to the weight. Both torques have to be equal so that the ruler can balance, so if the force of the right side is 100g=1N, and the lever arm is 10cm then the torque is 10Ncm.
We then started our experiment in finding out the weight of the ruler. We set up the exact same experiment at the top. Our point of balance was at the 70 cm point, so the left side had a force of 0.98N and a lever arm of 30cm and the right side had a lever arm of 20 and a unknown force. We found the force by 0.98*30= 29.4, then divided 29.4 by 20 to give us 'x', and that was 1.47. We then divided 1.47 by 9.8 so that we can convert it back to kg and got 0.15kg = 150g.
