Yet Another Projectile Motion Demonstration

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Well, partially just for fun, here is a program demonstrating projectile motion in 3-D. Can you notice that accelerations only occur vertically, and that the horizontal velocities are constant?

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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.

Of course, the force of gravity, or F_g, 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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