Projectile Motion*

The major conclusions reached in the analysis of projectile motion (air resistance neglected) may be summarized as follows:

1. The horizontal velocity of a projectile is constant. The projectile thus travels equal distances in a horizontal direction in equal intervals of time. 2. The vertical velocity of a projectile is constantly changing due to the influence of gravity. The projectile thus travels unequal distances in a vertical direction in equal intervals of time. 3. The constant horizontal velocity and constantly changing vertical velocity of a projectile cause it to follow a parabolic flight path (or trajectory). 4. The horizontal range of a projectile depends on its horizontal velocity and its time of flight. 5. The time of flight of a projectile depends upon its vertical velocity at release (or takeoff) and the relative height of release – that is, the difference between the height at which it was released and the height at which it landed. 6. The horizontal range of a projectile – and all other characteristics of its motion – are determined by its speed, angle, and relative height of release. 7. For maximum range, the optimum angle of release is 45 degrees if release and landing are at the same height, less than 45 degrees if release is at a greater height than landing, and more than 45 degrees if release is at a lesser height than landing. [This assumes that in each case that the magnitude of the velocity vector is the same. This may not be true in human performance because a performer may achieve different maximum magnitudes at different angles of release.] 8. In general, the speed of release exerts a greater influence on the range obtained than do either the angle or the relative height of release.

* This information was taken from Biomechanics of Sports Techniques, James G. Hay, 1973, Prentice-Hall