unit reflection

The new unit began by introducing the new terms of tangential and rotational velocity and determining their differences. Rotational velocity is measured in rpm (rotations per minute) and measures the amount of rotations an object has every minute. Tangential velocity is determined by distance over time. We learned real life examples of rotational velocity by with the carousel. Though all the machinery animals move at the same rotational velocity or rpm those who move on the outside have a larger tangential velocity because they have more distance to cover in the same amount of time. Also, we learned about the importance of rotational velocity and tangential velocity in train wheels, because the wheels on a train are tapered. If the wheels need to curve or self-correct, because the outer part of the wheel is smaller and on the outside, it will have the same rotational speed, causing the train to steer in swivels.
Here is a cool video that help explains railroad tracks!

Next we learned about rotational inertia. We defined rotational inertia as the tendency of an object to resist changes in rotation. It is dependent on mass and velocity. In particular, is is dependent on where the mass is located. Mass nearer the center or axis of rotation it decreases rotational inertia, and increases the ability to spin. That is why dancers pull their arms closer to their core when they spin.

After learning about rotational inertia, we learned about the conservation of angular momentum which is most easily explained through the formula Rotational Inertia times rotational velocity. Therefore, the momentum of a rotating object before is equal to the momentum of the rotating object after.

Next we learned about torque, or what causes the rotation of an object. Torque is determined by lever arm x force. Therefore, the larger the force or the lever arm, the more likely an object will spin.

Then we learned about Center of Mass, the average center position of the mass of an object, and Center of Gravity which is defined as the average position of weight within an object. In order for an object to be balanced its center of gravity must be within its basis of support or center of mass. Another way to increase stability is to lower your center of gravity or increase your basis of support. This is why wrestlers bend their knees and spread their legs when in a wrestling tournament.

Finally we learned about centripital force which is the center seeking force that pulls you into a circular rotation. When you are in a car and you make a sharp right turn, Centripital force is the only force acting upon you, your tendency to go in the opposite direction is not a force but inertia.



All in all, This unit required a lot of digesting, and some of the material had to resonate over a period of time before it sunk in (train wheels). I believe I should have asked more questions due to my problem was lack of understanding and lack of communication in this unit, but no worries. I think I grasped it in the end.

Physics in measurement

How do you find the mass of a meter stick, only using one 100g weight? The key is physics. Firstly you place your meter stick on a table surface, until the meterstick is completely balanced. Record where it meets the table. Do the same thing again, but apply the weight to the meterstick. Measure again where the meterstick meets the table. This will provide you with the lever arm. Since the meter stick is about 100cm long, you can assume the center of gravity is around the 50 cm mark. Next subtract the distance of the lever arm from the center of gravity to find the other meter stick's center of gravity. Finally, knowing the torque is always the same in the meter stick, you use the formula force times lever arm = force times lever arm to plug in your aquired results. Then you use algebra to solve for the mass of the meterstick!

Ultimate Physics Tutor - Sample 3 - Torque

Experiment to demonstrate conservation of angular momentum

This shows how weight distribution manipulates the conservation of angular momentum.