Before and After

I felt that it was necessary to write my blog about Thanksgiving. I'm sorry my videos are sideways :( Anyway, the video on the left is before, and the video on the right is after. The rest is pretty self explanatory. As you can see, after eating her delicious Thanksgiving dinner, my cousin is too full to do anything. In the second video, when my cousin lies down on the ground, her velocity becomes zero as does her acceleration. If I were to draw a free body diagram of her, the two forces would be mg, pointing down, and normal force, pointing up. They would be equal since the net force is zero. We should have weighed ourselves before and after to see how much the mg force increased by. My bet is 10 Newtons.

To relate this to chapter 14, when my cousin is standing up, like in the first video, the pressure she exerts on the ground is much greater than the pressure she exerts on the ground in the second video when she lies down. This is because the surface area of her feet in the first video is much smaller than the surface area of her body in the second video, and pressure=force/surface area.

A Swing

On Friday we had our fall orchestra concert at Mamiya Theater. It was pretty awesome because we all got out of school at 2:15 :) After we were done rehearsing, Richard, Colin, Leslie and me took a walk and explored the St. Louis/Chaminade campus. As you can see in the picture, we found a swing! It was really fun, but it made Colin and Richard feel sick :( At first, only Leslie and me were swinging on it. When Colin and Richard joined us, I asked, "What is the new mg?" and "What is the tension?". It was then that I realized just how much taking AP Physics B has influenced my everyday life. Never before would I have asked these questions. And then I realized that I could use this for my physics blog, so I took a picture :)

For simplicities sake, lets combine Richard, Colin and Leslie into one mass weighing a total of 300 pounds. That means that the mg force equals 2940 N. Because the net force in the y direction equals zero, The normal force plus the y components of the tensions also equals 2940N. The net force in the x direction also equals zero, (unless they are swinging side-to-side) so the x components of the tension must equal each other. In order to swing, Richard, Colin and Leslie must push off from the ground, which in itself involves even more physics. So much physics, so little time! But here is a brief summary for your enjoyment. :)

Rotational Dynamics - Door Handles

This morning, as I was trying to figure out what to write for my blog, I came up with the brilliant idea to make a video of my front door! It provides a perfect example of rotational dynamics. Torque is a force that causes or opposes rotation, and it is equal to the force times the distance from the axis to the force. T=rF. In this case, the force is applied perpendicularly, so if I wanted to calculate the torque value, I would not have to use trig. In this video, my hand applies the force and the distance to the axis is the distance from my hand to where the lock is, which is the point around which the door handle rotates. So lets say my hand applies a force of 20 N and the distance from the axis to the force is 0.05 m. Multiplying these two values together would give you the torque value, which is this case equals 1 N*m. the torque would have a negative value because the door handle is moving in the clockwise direction, so it actually equals -1 N*m . Here is an example of torque found in my everyday life. Until next week :)

The Common Cold

Germs surround us. While viruses and bacteria do not spread as quickly here in Hawaii as they do in big cities such as New York City (see picture from my trip two summers ago), there are still ever present. Quite unfortunately, I have been sick for the past six days. As I sat in my room trying to figure out what to write my blog about, I couldn't really think of anything because my activities have been greatly limited these past several days. So I decided to somehow figure out a way to relate the common cold to physics, and the only way I could think of doing so was through biophysics, even though I did not really know what biophysics was. After googling "biophysics," I discovered that this is actually a very broad term that encompasses biology, chemistry and physics. One website I found said that biophysics, "explains the biological function of cells, tissues, and organisms in terms of the structure and behavior of biological molecules." (http://www.biophysics.org) I also googled the causes of the common cold so that I could figure out a way to somehow link the two. Cold viruses are the main cause of the common cold. We all learned about viruses in 9th grade. Basically, a virus attaches on to a host cell and releases its genes into that cell.

Now for my primitive attempt to relate all of this to biophysics: Genes reflect the molecular structure of the DNA from which they are made, as seen with the virus's genes. Also, after your body has been infected by a virus, your immune system kicks in. The immune system contains many inflammatory mediators that are released when your body is infected with a cold virus. The function of these inflammatory mediators reflect the molecular structures of the proteins from which they are made. I wish my inflammatory mediators would hurry up the recovery process!!!

JU-NI-OR-SS.

I'm sure all the Juniors would agree with me that this years homecoming was the best EVER. Our lip sync owned and our cheer was awesome :) I've watched the videos of both numerous times on facebook. They're just so good (sigh) The homecoming game was the perfect way to end the week. It was fun and I had the opportunity to spend quality time with some of my friends, hence the picture.

As with all other sports, there are many physics concepts involved in the game of football. Projectile motion, forces, momentum, impulse and collisions to name a few. Projectile motion can be seen in the path of the ball when the quarterback throws it to a fellow teammate.  It seems that football is a game of collisions. In this game, people purposefully run into each other over and over again.  This is why football players must wear heavy padding to protect their bodies.  They collide with a lot of force! You could calculate the momentum of an individual football player if you knew their mass and velocity since p=mv. You could also calculate the impulse when they collide, in a variety of ways actually since J=F△t=△P=m△v. Probably the easiest way would be to find their change in velocity and then multiply that by their mass.   

Gosh I still feel pumped up from last week! It was sheer awesomeness. Now back to regular school :(