what is the need to study projectile motion in future for what it is used
Answers
Others have noted the actual cases where projectile motion occurs or the concept can be used to understand physical phenomena.
However, the real purpose of the study of projectile motion is that it is a good way to practice (and learn) some aspects of general problem solving and understanding (often) novel concepts in physics.
For instance, a lot of people will casually think that an object thrown straight up at speed X, and an object thrown up at an angle (with the same vertical speed) will land at different times. Studying projectile motion opens the door to understanding vectors (for both force and motion), and to realizing that orthogonal vectors can be separated and treated independently (removing the jargon: that vertical and horizontal forces and motion can be treated separately - and don’t interact with each other.)
It helps tremendously that anybody can study the motion of a ball or a rock with some simple tools (a measuring tool and a stopwatch, along with a study partner.) This makes it possible to learn that some physical phenomena have simple formula that describe them, and, very importantly for future problem solving, that a wide range of problems can be understood through a few simple formulas.
So, aside from what is actually being studied “on the surface” about projectile motion (i.e. what it is, how it works, where it applies & how), it serves to help to teach students about generalizations, about how concepts can be applied to a range of (seemingly different) problems, and about how some concepts of classical mechanics (and some math too) can be simplified to a handful of formulas that are then applied to each situation. HTH.