Projectile motion without air resistance Does the mass of projectile affect its trajectory when it is projected in no air resistance environment and why?
 A: No, the mass affects nothing; only the initial velocity, angle of projection and acceleration due to gravity determine the trajectory the projectile takes.
This is because the inertial mass $m_i$ which appears in $F=m_ia$ is equal to the gravitational mass $m_g$ which appears in $F=m_gGM/R^2$ of Newton's gravitational law. These two cancel in all your equations. This property of masses is one way of stating Einstein's Equivalence Principle.
A: It will only significantly affect the trajectory if the mass of the projectile is significant compared to the mass of the planet or other body providing the gravity.
For example, Earth's mass is $6 \times 10^{24}$ kg, so even a large aircraft or spacecraft of $10^6$ or $10^7$ kg will not have a measurably different trajectory because of its mass. However, the Moon is $7 \times 10^{22}$ kg, so its trajectory is measurably different from what it would be if it were massless.
See Don't heavier objects actually fall faster because they exert their own gravity?
