Newton made a unique observation by recognizing that all objects in free fall accelerate at the same rate.
When something is in 'free fall', the only force acting on it is gravity's pull. By definition, a projectile is a freely falling object. Therefore, all projectiles accelerate at 9.8 m/s/s toward Earth's center. gEarth = 9.8 m/s/s or about 10 m/s/s downward |
Next, we can generalize Newton's observation about Free Fall to create a mathematical model of the motion of freely falling objects in terms of their starting velocity (vi), their starting height (y) and the time in the air (t).