Yet another projectile motion demonstration...
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Well, partially just for fun, here is a Java applet demonstrating projectile motion in 3-D. Can you notice that accelerations only occur vertically, and that the horizontal velocities are constant?
Above is a three dimensional rotating view of an object in ordinary projectile motion, no air resistance. The trajectory is drawn in white. Periodically along its flight a set of x, y, and z axes is drawn in red, blue, and green colors respectively.
Musical accompaniment may be procured to the left.
Of course, the force of gravity, or Fg, pulls downward. Thus projectile experiences a vertical force aimed downward along the y direction. There are no forces pulling along the x or z directions. Therefore, the projectile will accelerate in the y direction due to the pull of gravity; it will not accelerate in the x or z directions, since there are no forces in those directions.
Remember that when an acceleration occurs, a velocity must change. So, the projectile changes velocity in the y direction; it does not change velocity in the x or z directions.
Notice that in the above demonstration the y-axes, all colored green, are spaced equally as time passes during the flight of the projectile. These axes mark the x, z motion of the projectile. There is no acceleration in the x or the z directions for this motion, and, therefore, there is no change in velocity in these directions. So, the projectile travels through equal distances in equal time intervals along the x and z directions. The resulting path that is projected on to the x, z plane is a straight line. The set of y-axes, i. e., the green lines, mark this linear path.
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