Table of Contents
Horizontal Projectile Motion
Horizontal projectile motion occurs when an object is launched horizontally from a height with no initial vertical velocity. The horizontal and vertical motions are independent: the object moves at constant horizontal velocity while simultaneously accelerating downward due to gravity. This creates a parabolic trajectory.
Classic examples include a ball rolling off a table, a bullet fired horizontally, or a package dropped from an aircraft. The key insight is that the time of flight depends only on the height and gravity, not on the horizontal speed. A faster horizontal speed simply means the object travels farther before hitting the ground.
Motion Equations
Example Trajectories
| Height (m) | v₀ (m/s) | Time (s) | Range (m) |
|---|---|---|---|
| 1 | 5 | 0.45 | 2.26 |
| 5 | 10 | 1.01 | 10.1 |
| 10 | 20 | 1.43 | 28.6 |
| 100 | 50 | 4.52 | 225.8 |
Frequently Asked Questions
Why does horizontal speed not affect fall time?
Gravity only acts vertically, so it only affects vertical motion. The horizontal and vertical components of motion are completely independent in the absence of air resistance. Whether you drop a ball or throw it horizontally at 100 m/s, both hit the ground at exactly the same time from the same height.
How does air resistance change the result?
Air resistance reduces both horizontal distance and alters the trajectory from a perfect parabola. The horizontal velocity decreases over time (drag), while the vertical terminal velocity limits the falling speed. For dense, small objects at moderate speeds, air resistance is negligible. For light objects or high speeds, it significantly reduces range and time of flight.