Contact Lenses and Reflection

I didn’t really experience anything exciting that was physics-related this week; however, when I was putting in my contacts this morning, I remembered that we are learning about lenses. I always wanted to know how contact lenses worked ever since I got them because my vision improved dramatically when I got contacts. I’m nearsighted, which means that my eyes can’t focus on far away objects because the light rays converge in front of the retinas in my eyes. Therefore, I need diverging lenses in order to help me see faraway things because diverging lenses make the light rays diverge a little more so that they can converge farther away, at the retinas. When I was looking at my contacts, I also realized that they are fatter at the edges than at the center, just like our textbook says about diverging lenses for nearsightedness. When I was taking the picture of my contacts for this blog, I also realized that I was in front of a plane mirror, and since we are also learning about reflection, I decided to incorporate the image of my contact lenses in the picture.

A Convection Oven

I was using a convection oven to cook French bread pizza for lunch today, and it occurred to me that I never knew how it works (besides that it cooks my food faster than a regular oven). What are the physics behind it that power it and heat up my food? I decided to look that up and find out for myself. I found out that “convection” is the movement of molecules, and the process of convective heat transfer occurs through diffusion, the random movement of particles. Heat transfer works by the transition of thermal energy, and we learned that heat always flows from the hotter object to the colder one. Forced convection is the heat transfer of a fluid that is not induced by a natural heating force. This is the type of convection that powers a convection oven. In a convection oven, a fan is turned on and spins quickly so that the heat it produces is used to heat up the food. In this case, the heat from the fan is transferred to the food and heats it up because the food is colder than the fan. Who knew you could learn so much about physics by just making your lunch.

Bobsledding

Last night, I was watching a little of the Olympics. Bobsledding came on and although I’m usually bored by bobsledding, I decided to watch it because a U.S. team was about to go. The first U.S. team was kind of disappointing because they tipped over on their side at the end, costing them big time. However, the last team was another U.S. team, and they did outstanding, so I think they got gold. They apparently got first by 0.04 seconds, a miniscule amount of time. When the announcer was explaining how they went so fast, physics popped into mind. He said that what go them the fastest time was that all the bobsledders on that team kept their heads super low. This was the factor that sped them up because there’s a natural G-force that is trying to pull them up, but they did a good job of opposing that force by staying so low. By keeping low, they also cut down a lot on their air resistance, which helped to cut down their time. I learned something about bobsledding while the announcer explained the “G-force”. I knew that the bobsledders kept low to avoid air resistance, but I didn’t know that a G-force was also pulling them up at the same time, making it harder for them to go as fast as they can.

Winter Olympics

Since I've been watching the Winter Olympics as much as possible, I realized that there is quite a bit of physics involved in many of the events of the Winter Olympics. In fact, in some of the events, physics plays a major role in how well you do; one little mistake in your movements can cost you a medal. When I was watching Apollo Ohno in the speed skating final yesterday, he said that if he hadn't had that one little slip, then he could've won gold, but he came up short and got bronze because of that one mistake that slowed him down. In addition, in all the downhill sledding sports such as luge, bobsled, and skeleton, any little movements away from the center can cause air resistance and slow you down. The announcers even said that a little mistake at the top can be more costly than a smaller one at the bottom of the track because you don't have much speed yet at the top. While watching ski jumping, I was wondering why the skiiers bodies get so paralled to their skis, and I deduced that there is physics involved in this technique. I thought that they get as parallel to their skis as they can because it causes less air resistance, allowing them to jump farther. Overall, the Winter Olympic games involve a lot of air resistance, velocity, and momentum.

The Physics in Rides

I was so busy this past weekend that I had no time to go to the Punahou Carnival (which, I suppose, can be a good thing since I go to Iolani). However, thinking about the carnival made me get the idea of writing my physics blog about the physics in carnival rides. For instance, the Swings and the Ferris Wheel are good examples of uniform circular motion. On both rides, you sit in something as it goes around in a circle at a constant speed but constantly changing velocity. Pharaoh’s Fury is an example of a ride that moves like a pendulum. It goes back and forth, has its greatest velocity at the bottom, and its least velocity at the top of either side. Ring of Fire is a roller coaster, which demonstrates acceleration. After the roller coaster is released from rest at the top, it accelerates at a constantly rate downward and then decelerates at a constant rate back to the top. These are just a few examples of physics is carnival rides, but all rides have some kind of physics involved in them.

Power in Tennis

I didn’t experience anything interesting this weekend, so I have to talk about tennis again. Yesterday, in my tennis lesson, I learned how to hit through the ball more. When my tennis coach says to “hit through the ball”, he means to use your body more to hit a heavier and deeper ball. The most important thing I learned was that by leaning forward when you hit the ball, you can put more power on the ball, which makes it heavier and faster. Leaning forward also gives you more momentum while you are hitting the ball. In addition, it keeps the ball from flying up, which gives it a more direct, straight shot. Another important thing I was practicing was bending down low and staying low while I hit the ball. This also puts more power on the ball because you get more power by using your legs. Last of all, another key to hitting through the ball is setting up quickly and then rotating your body. This creates torque and also puts more power on the ball. All in all, keeping physics in mind while you are playing tennis can really make a difference in how you hit the ball.

Friction in Tennis?

I bought a new pair of tennis shoes that I had never tried before. Of course, all shoes are built differently, so they are going to feel differently too. This shoe in particular rises up high by my ankle and cuts into my foot. I discovered that in combination with this design, the shoe is also kind of stiff and hard in that area. This was not a good combination and resulted in rubbing my skin raw. I felt a pain just in front of my ankle, and I deduced that due to the force of friction between my shoe and my skin, the shoe was rubbing my skin off. I decided that to cut down the friction between my already raw skin and my shoe, I should wear higher socks and put tape over my skin to protect it from the force of friction. Similarly, when I used my coach’s racket one time, his grip was tough because it was made of leather, and it gave me a blister. This is also largely due to the friction between the grip and my hand. My hand hurt the most when I was hitting forehands because that’s when I turn my hand on the grip the most, causing more friction to occur. I never knew there could be so much friction in tennis, and I unfortunately discovered this by getting sores on my hands and feet.