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.