Kinematics · 26 min
Free Fall & Projectile Motion
Two directions, completely independent, happening at once.
Why should I care?
If you drop one ball straight down and launch another sideways from the same height at the same instant, which one hits the ground first?
They land at the same time. Horizontal motion and vertical motion don't interfere with each other — the sideways velocity never affects how fast the ball falls.
Explore
Trace the parabola
Adjust launch angle and speed, and watch the horizontal and vertical components trace out separately before combining into the familiar parabolic path.
The idea
Independence of motion
Projectile motion is two separate 1D motions happening simultaneously: constant horizontal velocity (no acceleration, ignoring air resistance) and vertical motion under constant acceleration due to gravity. Solve each axis with SUVAT separately, then combine.
True or false?
A faster horizontal launch speed makes a projectile fall to the ground more slowly.
Worked example
Worked example
A ball is launched horizontally at 12 m/s from a 20 m cliff. Find the time to land and the horizontal distance travelled. (g = 9.8 m/s²)
- 1
Vertical motion only decides fall time: y = ½gt².
Your turn
What determines how long a projectile launched horizontally stays in the air?