Sports Physics & Biomechanics ★★☆ Moderate

⚽ Football Kick Physics — Trajectory & Spin

Simulate a football free kick with drag and Magnus lift. Adjust launch angle, speed, and topspin/backspin/sidespin to curve the ball around a wall and into the top corner. Visualise the full 3D trajectory.

Range: — Max Height: — Flight Time: — Lateral Drift: — Result: —
17°
28 m/s
0 rad/s
0 rad/s
9 m

How to use

Set your angle, speed, and spin, then press Kick! to launch the ball. The green wall represents the defensive wall at the set distance. The goal is 25 m away. Sidespin curves the ball left/right (Magnus effect). Backspin (negative) lifts the ball; Topspin (positive) dips it faster. Try the Banana Shot preset to see a classic curling free kick!

The Physics

Equations of motion: m·a = F_drag + F_Magnus + mg. F_drag = −½ρv²C_d·A·v̂. F_Magnus = ½ρ·C_L·A·v² · (ω̂ × v̂), where C_L ≈ 0.2–0.5 depending on spin rate ω. The "banana shot" uses sidespin ω_z giving lateral deflection Δy ∝ C_L·v·d/g. Optimal free-kick angle balancing distance and clearance ≈ 16–18° for 25 m.

About this simulation

This simulator integrates a football's full equations of motion — gravity, air drag and Magnus lift — frame by frame to show exactly how launch angle, speed and spin shape a free kick. Sidespin bends the ball's path sideways around a defensive wall the way a real "banana shot" curls into the corner, while topspin dips it down faster and backspin holds it up longer, letting you chip it over the wall instead of around it. Adjust every parameter yourself or load a named preset to see the trajectory, drift and result update instantly.

🔬 What it shows

A side-view trajectory coloured from launch to landing plus a top-down inset tracking lateral curve, with a defensive wall and goal frame drawn to real dimensions (7.32 m wide, 2.44 m high, 25 m away) so you can see exactly whether a shot clears the wall and finds the net.

🎮 How to use

Adjust launch angle, initial speed, topspin/backspin, sidespin and wall distance, then press Kick! to animate the flight, or jump straight to a preset (Free Kick, Banana Shot, Knuckleball, Chip & Lob) to see range, max height, flight time, lateral drift and the shot result.

💡 Did you know?

A true knuckleball uses almost zero spin on purpose — with the ball barely rotating, the airflow separates unevenly and randomly off its seams, making the flight path wobble unpredictably rather than curve smoothly, which is exactly why goalkeepers dread it.

Frequently asked questions

What is the Magnus effect?

It's the sideways or vertical force generated when a spinning ball moves through air — the spin drags air around with it, creating a pressure difference across the ball that pushes it perpendicular to its direction of travel. Sidespin curves the ball left or right; topspin and backspin push it down or lift it.

Why does sidespin create a "banana" curve?

Sidespin makes the ball's Magnus force act sideways throughout its flight, continuously bending its path in one direction. Because the force builds up over the whole trajectory rather than acting once, the path curves progressively more, producing the classic banana-shaped arc that bends around a wall late in flight.

Why does backspin make the ball fly further and stay up longer?

Backspin generates a Magnus lift force that partly opposes gravity, so the ball falls more slowly than it would without spin — this extra hang time is why the "Chip & Lob" preset combines a steep angle with negative (backspin) values.

What is the optimal launch angle for a 25 m free kick?

According to the physics used here, roughly 16–18° balances covering the distance to goal against clearing a defensive wall standing a few metres in front — much steeper and the ball loses too much forward speed; much flatter and it can't get over the wall.

Why does air drag matter for a football's flight?

Drag force grows with the square of speed, so a fast-struck ball loses a significant fraction of its velocity to air resistance over its flight, shortening the range and flattening the trajectory compared to what gravity alone would produce.