The Weather Outside Is Frightening

Although its too late for the extra credit, my bi-monthly moment of physics enlightenment is represented in this really blurry, from a blackberry camera, picture which was taken saturday afternoon when i was picking up a friend, who was too busy to take this picture for me so i had to take it while driving my manual car in the ridiculous storm. If its not obvious, this picture is of a banked turn going down alewa heights (it hit me goin up but i didnt hav the phone ready to take it), and is a good example of the effects of banking turns, versus completely level turns. First of all, centripetal force is any force that makes an object move in a circular path directed towards the center, for example: gravity, friction, normal force, tension. When taking a banked turn, the centripetal force exerted on your car is normal force, or n, which due to the slope is directed toward the center, as opposed to friction, or (mu)(n), and therefore (thankfully in this case, or else i would have overcome the centripetal force and gone off tangent and hit that acura) the centripetal force is greater, which allows you to take the turn with more speed safely. Another example of physics i encountered that evening was when a car very far in front of me began to hydroplane after it applied too much braking force on and the wet road and thus broke traction with the road and thankfully wasn't hurt. Another example of physics that I was tempted to (but not even close to considering) try was an intentional breaking of traction (see 2 posts below), which relies on the breaking of traction, friction, and momentum to intentionally slide the car. On another note, let it be known that my physics journal for this week does not include the stop short or mr. k's other "sneaky physics."

Whie My Guitar Gently Weeps

On Sunday, in my frantic search of my wallet, and subconciously a physics topic for the journal I had yet to do, I paced around my messy room just minutes before my ride arrived to take me to Mid-Pac's version of RENT, which was outstanding. As I called to various family members and inquired about my wallet I got an answer from my mom, and as I began to reply I unknowingly ran straight into my upright guitar case and fell over, pretty much tackling it. After the initial skip of a heart beat and fear that I had destroyed my Les Paul I realized I had found my topic for this week's journal! My almost heart-breaking incident represents a (most likely) inelastic, "sticky" collision. If I perhaps knew the velocity at which I ran into my guitar I could easily find out the velocity of both me and my Les Paul right after the collision, since in this case m1v1 + m2v2 = (m1+m2)vf, and I could easily figure out the mass of myself and the guitar, which would allow me to do the problem, assuming it were an ideal situation. What allows me to do so is the Conservation of Momentum, or Newton's Second Law of Motion, which essentially states that the momentum (mv) of a system before collision is equal to the momentum after the collision because objects transfer momentum when they contact. So while the guitar was not moving, and technically had no momentum because it had no velocity, my combined velocity and mass was transfered into it when i ran into it, which caused it to gain velocity and fall with me to the ground. Also, the impulse on both me and the guitar was equal, and could be computed if the intial and final velocities were obtained. Impulse is the momentary force exerted on each object after collisions that is equal to the change in momentum. While I caused the guitar to go from rest to motion, the guitar exerted a slight force on me as well that decreased my velocity, atleast momentarily before i fell.

Drift! Drift! Drift!

Touching back on old topics, this picture was taken in Japan at an open invitational to promote the American Formula D in Japan. Pictured here is Team Signal Auto's Nissan Skyline R34 drifting through a turn, and when i stumbled upon it when searching through photos I began to appreciate the physics involved. Drifting, if you haven't seen Tokyo Drift or Initial D, is a style of driving where the driver intentionally causes the car to break traction with the road, forcing the car into a slide, and is essentially based on inertia and momentum, and is greatly related to the effects of friction. Newton's First Law of Motion, which explains inertia, states that an object in motion will stay in motion and maintain the same direction, or an object at rest will stay at rest. Momentum is essentially Newton's Second Law of Motion, that states that the net force on an object is equal to the mass of the object multiplied by its acceleration. To get the car sliding, drifters employ various techniques; beginning techniques use the e-brake and cluth or shifting through gears to cause the back wheels to lose traction with the ground, and then steer the car to lead it where they want to slide it. The property of inertia allows the car to continue to slide, while the change in steering angle and the gradual press of the gas provides the external force to control the direction of the slide. The massive clouds of smoke commonly associated with drifting that provide lots of the entertainment are caused by the friction between the tires and the road, another external force that opposes the inertia of the vehicle. More advanced drifters employ more challenging techniques that manipulate momentum. As the vehicle continues to accelerate, the driver throws the car into the turn and quickly countersteers (power over/feint). The first turn in shifts the car's weight and speed towards the corner, and the immediate countering causes the car to slide because of the great shift in the direction of momentum. Since the properties of drifting require extra turning and braking in order to get the car sliding, as well as a great amount of friction on the back tires, it is not ideal when racing, but it is definately the most entertaining form of motorsports to watch.

Feelings About the First Quarter

When browsing through all my photos and digital art trying to find a picture that accurately represented my feelings about physics so far, i stumbled upon this photo i had taken that depicts me and several of my japanese classmates viewing the fireworks that celebrated a local matsuri this summer in Japan, and the similarities between it and my first quarter of physics became apparent. To get this picture the way i wanted (with myself in it, middle right) a lot of preparation was involved, more so than i had originally planned on. When setting up the camera I came in with notions that I already knew how to work the camera (if my analogy to physics isnt clear, since i have worked on my car and my uncle runs charts and works with aerodynamics, etc. i thought i had a decent understanding of physics) i would easily be able to get nice shots. However, firework pictures was a completely unknown topic to me, and required a lot of trial and error before i finally could get it right. At one point, despite my love of fireworks and photography, i found myself frustrated by my inability to take the quality of pictures i wanted, but realized that i had to approach it with a fresh slate, and found that i was able to understand mechanics behind successful firework shots, like delayed exposure, etc.
So in relation to physics, I came into the course already interested, yet was slightly discouraged after the first test. At the beginning topics seemed like the fireworks in that they were sometimes hard to capture until i realized i had to approach learning it with a different attitude. However, after approaching it with a different attitude i found my grade improving and that i was learning more and more about topics that interest me. I admit that my effort at the beginning of the year wasn't all there, and i think i'm working harder and harder. After looking back, i realize that i'm not doing as well as i had pictured myself as doing, but now i see the big picture that i couldn't see before. My goals for this course were never primarily the A (although that would be nice), but to understand and capture topics that i really am interested in and love, just like fireworks.

Hawaiian Brian's

This picture, taken at the Class of 2010 Welcome Back Event at Hawaiian Brians, is a picture of me about to serve a ping pong ball and demonstate the properties of a projectile. A projectile, an object that is only acted upon by gravity, is exemplified by the ping pong ball because after it is hit it maintains a constant horizontal velocity, while gravity causes it to travel in a parabolic arc as its positive velocity is slowed by gravity, peaks at 0 m/s, and then accelerates downwards back to the table, all of which is repeated multiple times throughout a rally. A ping pong ball is a projectile because after it is hit, there is no forces acting upon it (ie. jets, etc.) except for gravity. In addition, at Hawaiian Brian's I also played pool (no pictures, unfortunately), which helped to demonstrate Newton's First Law, in which an object tends to remain in its state of motion unless an external force acts upon it, as well as Newton's Third Law, that states that every action has an equal and opposite reaction. Unless the ball is hit by the cue, it will remain still at equilibrium, in which only gravity is causing it to push against the table, and the table is pushing upwards with the same force, and assuming the pool table was really big and friction was not a factor, the ball would continue to accelerate at the same rate after being hit by a cue. Newton's Third Law applies when the ball is hit with varying forces, whether i wanted to tap a ball in from 3 inches away, or try to bank a shot from across the table, the different amounts of force applied results in a different acceleration.

Physics Journal #2

This picture, for demonstative purposes only, represents a rather fortunate accident that occured to me on Saturday. While i was rushing to pack up my guitars and amp to head to a friend's house to jam i spun suddenly when i heard the house phone ring, swinging the guitar on my back and accidently sweeping both my cell phone and my cup of Mitsuya Cider off the table. As i stood back, (as i look back on it, surprisingly calm at this potentially depressing incident) i did not see possible destruction of my phone, but the two objects falling at the same speed (ignoring air resistance, -9.8 m/s) and hitting the ground at (almost) exactly the same time. This is because everything on Earth is equally affected by the presence of gravity during free fall, which causes all objects, no matter their size or weight, to accelerate at -9.8 m/s, assuming air resistance is not a factor. Although my cell phone was clearly lighter than the cup full of Mitsuya Cider, gravity caused them to accelerate at the same rate, so they both had the same velocity throughout the entire fall. This little incident helped me to grasp the concept of free falling, and helped reinforce the principal that all objects, no matter their weight, fall at the same rate (in a vacuum) because of gravity.

Physics Journal #1: Velocity and Acceleration

This picture was taken before I went to Titan Motorsports's "The Weekender" to watch my friend's car participate in the loudest exhaust challenge and to try to score some deals on parts for my car. If you consider my friend, the photographer, as the origin or the position sensor in our lab, my car is actually travelling at a negative velocity because velocity indicates both rate of motion AND direction, and can be found by dividing the total displacement by the time elapsed. My car is not slowing down as one might expect with a negative velocity, in fact it is maintaining a constant velocity, the velocity is negative because my displacement is negative since i started in the positive direction and drove toward my friend so he could take the shot.

As car enthusiasts, we constantly brag about our car's acceleration, and the people at the event were no different, but when everyone was talking i realized how often we misuse the term. Acceleration describes the change in velocity over time, so it includes both flooring the gas pedal, as well as depressing the brakes. Acceleration, which people do not realize, can also be a negative amount because it is derived from velocity, so either speeding up in the negative direction (like in the picture) or slowing down in the positive direction, like stopping at a stop light, yield a negative acceleration. Therefore positive acceleration can be derived from stepping on the gas pedal and going in the positive direction, as well as applying the brakes in the negative direction. So when we strapped our cars to the dynamometer to measure horsepower and torque, although the car's speedometer can register the speed the wheels are spinning at, techincally the car is neither accelerating nor achieving a change in velocity since there the car is staying in the same spot. At the end of the event, i drove home and after arriving i realized that while I had driven from town to Aiea and back (which was clearly indicated by the amount of gas i had left in the tank), my displacement indicates i actually had not moved at all, and therefore my average velocity and acceleration was 0, which was slightly disappointing.