Well, we are certainly off to a strong start in the spring semester of Physics. It was definitely hard to come back since we had truly done no work, but the experiments we preformed and the lessons we learned certainly made it a lot easier.
Ms. Lawrence started class off by asking us a question, "Which person will go faster, the person on the outside horse of a carousel or the person the very inside horse of a carousel. Instantly, my brain shut down. How were we supposed to know this? It was beyond any knowledge we had learned before. Thankfully, Ms. Lawrence explained to us that the answer can be answered in two ways. To answer the question, we had to look at both the rotational velocity and the tangential velocity. We learned that rotational velocity was measuring the rotations per minute, and tangential velocity measured the distance covered in a certain amount of time. In the case of rotational velocity, both people were going the same speed. However, when we examined the tangential velocity, we came to realize that the person on the outside was moving faster. This is because they had a greater amount of distance to cover in the same amount of time that the inside horse did. To give an example, recall the propeller experiment we preformed on the first day back to class.
Next, we watched a video on rotational inertia, and the conservation of rotational momentum. Recall that inertia is the property given when an object resists change in motion. Rotational inertia is basically the same thing with one difference: it is the property given to an object when it resists change in spin. This property is dependent on mass and the distribution of mass. If there is more weight towards the outside of the axis of rotation, then the object will be harder to turn. As an example, think of how runners bend their knees when they are running; this brings the mass closer to the axis of rotation and will ultimately decrease the rotational inertia. Next we have the conservation of rotational momentum. We figured out that rotational momentum is equal to the rotational inertia multiplied by the rotational velocity. We also came to the conclusion that for momentum to be conserved, the rotational momentum before would have to equal the rotational momentum after. We set this equation up just like we did last semester for the conservation of momentum. To learn about the conservation of rotational momentum, we watched a clip on a figure skater pulling her arms in when she spun, causing her to speed up. We figured out that when the figure skater has her arms and leg extended, the rotational inertia will be larger, causing the rotational velocity to be smaller. Looking at the opposite spectrum, when an ice skater tucks her arms and legs in, she decreases her rotational inertia which will ultimately cause her rotational velocity to increase.
The next subject we talked about was torque. We said that torque caused rotation, and was equal to the force multiplied by the lever arm; the lever arm is just a fancy way to say the distance from the axis of rotation. The larger the lever arm is, the greater the torque will be. To go along with this, we also learned about center of mass and center of gravity. The center of mass is the average position of the total mass on an object or objects. The center of gravity is when gravity is working on the center of mass. Finally, we said that when an object is in a state of balance, it is because the counter-clockwise torque is equal to the clockwise torque.
Finally, we learned about centripetal and centrifugal force. Centripetal force is a center seeking force; it is what keeps you moving into a curve. Centrifugal force is defined as a center fleeing force, but in reality isn't actually a force at all. It is used to describe that feeling you get when your driving into a curve, like you are about to be flung out of the car. In actuality, there is no force that does this to you.
I think the biggest challenge coming into this semester was trying to reprogram my brain back into a Physics-thinking mode. I had been so used to thinking mindlessly during break that is was a shock to come back to the classroom. However, my classmates and Ms. Lawrence made it easy on me by taking a slow start and building up from there. We also talked over questions we had.
In this first unit of the new semester, I feel like my problem-solving skills and effort have increased. I talk more in class and help my partners during labs. I even try to explain to other people that are confused what is going on. My patience has also improved. It is easy in homework questions to try and simply get everything done. However, in reality it pays more to put forth effort, and think through questions that might be confusing. While this definitely increases the time it takes to finish exercises in the book, it is worth it. Second, I feel that as an individual and as a class, our communication skills have improved. We make sure to ask questions when we have them, and even inquire from our neighbors about concepts we don't understand. Finally, I feel that I have started to be more creative in physics, as I think about every day things that pertain to the units we are learning at the time.
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