Projectile motion
High School
Definition
The curved path followed by an object that is launched into the air and then moves under the influence of gravity alone. Its motion can be analysed as a combination of constant horizontal velocity and vertical acceleration due to gravity.
Worked examples
A ball kicked at \(20\, \)m/s\(\) at \(30^\circ\) has horizontal velocity \(v_x = 17.3\, \)m/s\(\) (constant) and initial vertical velocity \(v_y = 10\, \)m/s\(\) (decreasing at \(9.8\, \)m/s\(^2\)).
Horizontal motion stays steady; vertical motion accelerates downward under gravity.
A stone thrown horizontally off a cliff follows a parabolic path because gravity pulls it down while it moves forward at constant speed.
Even with zero initial upward velocity, gravity curves the path into a projectile arc.
Common mistakes
- Horizontal velocity decreases as the projectile rises and falls → Horizontal velocity remains constant (ignoring air resistance) Gravity acts only vertically; it does not slow or speed the sideways motion.
- At the peak of flight, the projectile has zero velocity → At the peak, vertical velocity is zero but horizontal velocity is unchanged The object is still moving forward at the top of its arc.
- The path is a straight diagonal line → The path is a parabola (curved) Constant horizontal speed plus accelerating vertical motion produces a curve, not a line.
Where you'll use it next
You'll use projectile motion to solve problems in kinematics, analyze sports trajectories, and study orbital mechanics and ballistics in advanced physics and engineering courses.
Found in 1 StudyPug lesson
Projectile motion
11th Grade11thPhysics 11
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026