Android Open Source - FallApp Physics

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License

The source code is released under:

MIT License

Java Source Code

package ie.lc.fallApp;
/* w  ww  .  j  a v a 2s  .co  m*/




public class Physics
{
  private final static double secondsInHour    = 3600.0;
  private final static double typicalHumanMass = 80.0; // KG
  
  private static Planet activePlanet = Planet.earth;
  
  
  
  
  
  /**
   * Set the planet to consider in calculations.  Earth is the default.
   */
  public static void setActivePlanet( Planet p ) {
    activePlanet = p;
  }
  
  
  
  
  
  /**
   * Get planet currently used for computations.
   * @return Planet
   */
  public static Planet getActivePlanet() {
    return activePlanet;
  }
  
  
  
  
  
  /**
   * Compute equivalent fall height given velocity.
   * @param velocity Velocity in metres per second.
   * @return height in metres.
   */
  public static double computeEquivalentFallHeight( double velocity ) {
      double joules  = kineticEnergy( typicalHumanMass, velocity );
      return equivalentHeight( joules, typicalHumanMass, activePlanet.getSurfaceGravity() );
  }
  
  
  
  
  
  /**
   * Compute energy-equivalent velocity given height.
   * @param height Height in metres.
   * @return Velocity in metres per second.
   */
  public static double computeEquivalentVelocity( double height ) {
      double joules = potentialEnergy( height, typicalHumanMass, activePlanet.getSurfaceGravity() );
      return equivalentVelocity( joules, typicalHumanMass );
  }
  
  
  
  
  
  public static double kilometresPerHourToMetresPerSec( double kph ) {
    return (kph * 1000.0) / secondsInHour; 
  }
  
  
  
  
  
  public static double metresPerSecToKilometresPerHour( double mps ) {
    return (mps / 1000.0) * secondsInHour; 
  }
  
  
  
  
  
  /**
   * Compute kinetic energy given mass and velocity.
   * @param mass Mass in kilograms.
   * @param velocity Velocity in metres per second.
   * @return Energy in joules.
   */
  private static double kineticEnergy( double mass, double velocity ) {
      return 0.5 * mass * velocity * velocity;
  }
  
  
  
  
  
  /**
   * Compute equivalent height given energy, mass and gravity.
   * @param energy Energy in joules.
   * @param mass Mass in kilograms.
   * @param gravity Acceleration due to gravity in metres per second.
   * @return Height in metres.
   */
  private static double equivalentHeight( double energy, double mass, double gravity ) {
      return energy / (mass * gravity);
  }
  
  
  
  
  
  /**
   * Compute potential energy given height, mass and gravity.
   * @param height Height in metres.
   * @param mass Mass in kilograms.
   * @param gravity Acceleration due to gravity in metres per second.
   * @return Energy in joules.
   */
  private static double potentialEnergy( double height, double mass, double gravity ) {
      return height * mass * gravity;
  }
   
  
  
  
  
  /**
   * Compute equivalent velocity given energy and mass.
   * @param energy Energy in joules.
   * @param mass Mass in kilograms.
   * @return Velocity in metres per second.
   */
  private static double equivalentVelocity( double energy, double mass ) {
      return Math.sqrt( (2.0 * energy) / mass );
  }
}

Java Source Code List

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