# Vectors and Projectiles - Mission VP8 Detailed Help The acceleration of a projectile has the greatest (or smallest) magnitude ... Definition of a Projectile: A projectile is an object for which the only force acting upon it is gravity. The force of air resistance is negligibly small or nonexistent for a projectile. Forces, when unbalanced, cause objects to accelerate. The magnitude of the acceleration is directly proportional to the magnitude of the unbalanced force (a = Fnet/ m). If the magnitude of the net force is changing, then the acceleration will change as well. If the magnitude of the net force is constant, the acceleration will be a constant value. For a projectile, the unbalanced or net force is gravity. The magnitude of the force of gravity is dependent upon the mass of an object and the gravitational field constant (g)- see Formula Frenzy section The force of gravity (Fgrav) that acts upon an object is mathematically related to the mass of an object (m) by the equation:   Fgrav= mass • g   where g is the acceleration caused by gravity alone. The value of g on Earth is 9.8 m/s/s (approximately 10 m/s/s).  