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evan

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  1. evan
    There are two types of spin that a player can apply to a tennis ball, those being topspin and backspin. What prompted my thoughts on this idea would be my attendance of the University of Rochester tennis match today against Nazareth. As these advanced players made the ball skip and flip and kick every which way, my mind went crazy! :labmate)

    A topspin shot is hit by sliding the racquet up and over the ball as it is struck. By dragging the racquet over the ball, the friction between the racquet's strings and the ball is used to make the ball spin forward, towards the opponent. The shot dips down following impact with the court and also bounces at a lower angle than would a shot with no spin applied to it. As a ball travels towards a player after bouncing, it has natural topspin that is caused by the friction of the tennis court. When hitting a topspin shot, the player is reversing the spin of the ball, which requires more energy. This change in energy from potential to rotational kinetic energy allows the player to effectively execute the top spin shot.

    A backspin shot is hit in the opposite manner, by sliding the racquet underneath the ball as it is struck. This causes the ball to spin towards the player who just hit it as it travels away. What is very interesting about the back spin shot and has been proven by physicists all over the world is that hitting this shot requires only roughly about half of the raquet speed of a top spin shot, for to execute this shot the player does not change the rotation of the ball. The oncoming ball bounces off the court with topspin, spinning from top to bottom as it comes toward the player. When a player returns the ball with a slice shot the direction in which the ball spins around the axis of rotation is maintained. From the players perspective, it actually seems as if the ball is moving away from them.
  2. evan

    The Theory of Relativity

    By evan,

    The theory of relativity encompasses two theories of famous scientist Albert Einstein: special relativity and general relativity.
    Concepts introduced by the theories of relativity include:
    -Measurements of various quantities are relative to the velocities of observers. In particular, space and time can dilate.
    -Spacetime: space and time should be considered together and in relation to each other.
    -The speed of light is nonetheless invariant, the same for all observers.
    Some, and to many most of the things that the theory of relativity introduces seem absolutely insane to many of those who hear it, although as technology advances more and more tangible evidence is being gathered to support the theory. In the field of physics, relativity catalyzed and added an essential depth of knowledge to the science of elementary particles and their fundamental interactions, along with ushering in the nuclear age. With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves. However those are blogs of their own, so stay tuned.:love-struck:

    Special relativity is a theory of the structure of spacetime and is based on two main principles:
    -The laws of physics are the same for all observers in uniform motion relative to one another (principle of relativity).
    -The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the source of the light.

    General relativity is a theory of gravitation developed by Einstein in the years 1907-1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field are physically identical; something to which the simple mind would simply be insane. However when taken in to deep consideration, general relativity is really something interesting to think about.
  3. evan

    Warp Drive

    By evan,

    While I'm on a kick here (hard to guess what I find interesting right?), here's something I found on a totally different blog site about the possibilities of traveling faster than the speed of light. There is a very convincing theory, too bad no one knows where to get the energy....
    And yes FizziksGuy, it uses "string guess". I'm very sorry.
    Here's the link:
    http://news.discover...hip-engine.html
  4. evan

    We Have Lift-Off...

    By evan,

    I recently travled down to Iroquois middle school to take advantage of a non-windy day to launch my favorite model rocket, and explore some physics in the process. The winds were coming from the South at about 7 mph, so the East end of the field had to be utilized for the launch, and everything went flawlessly because of planning ahead in this fashion.
    Some specs of the solid fuel engine I used are as follows:
    The average impulse is 5N/sec
    Maximum thrust was 12.1N
    Time to rise was about 3 seconds including delay between when the engine stopped until parachute deployment
    Maximum altutude was about 400 feet

    With all these stats, I concluded that the initial velocity off the pad was approximately 80m/s!!!!! Good thing these model rockets are unmanned...
  5. evan
    Everyone knows what a sword is, whether it be a katana, claymore, or even the famed Excalibur of Arthurian tales. Sure when you swing a sword it cuts, but what about the sound it makes? This came to mind as I thought of one of my favorite movies, The Last Samurai. At first I related it to the sounds produced by whips or arrows, but I wanted to look into the matter to find out what is really behind the cause of a sword's sound.




    To go with the theme from The Last Samurai, I researched a lot about the ideas the Japanese associate with their swords. in Japan in order to have a proper sound, or hasuji, the blade must create the proper sword wind, or tachikaze. When a sword slices through the air, it must push away air molecules and creates what is called a thickness noise. This works in conjunction with loading noise, which is the blade having a direct effect on the air, generating forces to move it about. Since the blade of a katana is tapered, this allows it to cut the air more aerodynamically, and forms a vortex of air behind it, What you hear is the tone of the blade cutting through and pushing molecules out of the way, much like an arrow piercing the air as it flies by.

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