Final answer:
The maximum range of a projectile like an M120 mortar is typically reached at a 45° launch angle, neglecting air resistance. The real optimal angle is slightly less due to air resistance. Calculations generally ignore Earth's curvature, which is sufficient for short-range projectiles.
Step-by-step explanation:
The maximum range of the M120 120mm mortar or any projectile is achieved when it is fired at an angle of 45°, assuming no air resistance. In reality, air resistance affects the trajectory, and the optimal angle may be slightly less. The same range can be achieved with two different initial launch angles that add up to 90°; the one with the smaller angle has a lower maximum height compared to the larger angle.
When considering the curvature of the Earth, the surface at a distance will be lower than at the point of launch, which can affect the calculated range of a projectile. However, for most practical purposes, and especially for relatively short-range weapons like mortars, the assumption of a flat Earth is usually adequate.
Projectile motion equations do not typically account for factors like air resistance, thinning air with altitude, or Earth's curvature, but they are useful for an idealized understanding of trajectories and ranges.