Finding The Mass of a Meter Stick Lab

We had a lab this week to find the actual mass of the meter stick.

First we had to do a demo and place the meter stick on the table unbalanced and label the forces + lever arms like so:

Then we had to balance the meter stick on the table to find the centre of gravity and again label the forces and lever arms:

Here we found out that the centre of gravity for the meter stick was exactly at 50cm.

Now we added the 100g weight to the end of the meter stick and watch it become unbalance. Here we labeled the torques, forces, and lever arms.

Plan:

The Plan to find this mass of the meter stick was pretty simple. You have to know the conservation of torque and angular momentum, which is Force x lever arm= F x lever arm.

1. Convert the 100g weight into kg by multiplying by 1000. (We need kg to do the force equation)
2. Find where the centre of gravity and mass was of the meter stick alone. (50cm)
3. Convert the mass into force
4. Add the weight to end of meter stick
5. Balance the meter stick with the weight so it stays on the table
6. Find the new centre of mass which is where the edge of the table read on the meter stick (70cm for me)
7. Use the equation conservation of torque
8. Find the force of the meter stick side
9. Use w=mg to find mass of it in kg (150000)
10. Divide by 1000 to get grams (150)

Results:

My plan that I planned above actually went great. The meter stick with the weight balanced on the table at 70cm and the lever arm for the weight was 30 (100-70 because 70cm was the centre of mass). The lever arm for the meter stick was 20cm. Then found the force of the weight which was mass*9.8 (gravity) and got 980000. So I plugged them into the equation (Torque of Meter stick: F*20cm=980000*30cm:torque of side-weight). The final result of the force for the meter stick was 1470000. Then converted back into kg, then into g using the before equations. I was 6 grams away from the actual mass of the meter stick which was 144g. This is a demonstration/example of how things are balanced, they have counter and clockwise torques on both sides of them that balance out each other in the equation with their lever arms and Forces.

New Year - New Material

The beginning of this year we started off with some new things to learn and discuss about. We talked about torque and rotational inertia. Here are two videos that help explain them both:


In this torque video it explains the basis. Torque is based on two things: force and lever arm. Torque is, in basic terms, the force to turn/rotate an object, like a screw. Door stoppers also help explain this; the reason why we put them farther from the hinges is because the door stopper can only hold so much force, so it needs a bigger lever arm to proportion it.



In this video it shows two discs racing, one disc has mass farther from the centre axis and one with it closer. As you can see the one with the mass closer wins, this is a proof/example of rotational inertia. Rotational Inertia is how much an object wants to move/rotate with the mass closer or far from its centre axis. If mass is closer, then the rotational inertia is less, farther then bigger. If objects want to be rotated easier, then they would want their mass to be evenly spread out its body, which makes it have a low rotational inertia.