Home›Glossary›Free Fall

Free Fall

General

Free Fall (Physics)

Motion where gravity is the only force acting on an object, with no air resistance or other forces, governed by constant gravitational acceleration.

Definition

Free fall describes motion where gravity is the only force acting on an object — no air resistance, no other forces — making it the simplest and most idealized form of falling motion. It's governed entirely by gravitational acceleration (g = 9.8 m/s² on Earth), independent of the falling object's mass.

The Free Fall Calculator computes fall time, final velocity, and distance fallen from any single known value.

Formula

Velocity after time t: v = gt Distance fallen: d = ½gt² Velocity after falling distance d: v = √(2gd)

where g is 9.8 m/s² on Earth.

Worked Example

An object dropped from a 45-meter height (starting from rest) takes t = √(2 × 45 ÷ 9.8) ≈ 3.03 seconds to hit the ground, reaching a final velocity of v = 9.8 × 3.03 ≈ 29.7 m/s (about 107 km/h) just before impact.

Key Things to Know

  • Mass doesn't affect free fall rate: all objects accelerate at the same rate under gravity alone, regardless of how heavy they are.
  • Air resistance is what makes real-world falling different: a feather falls slower than a bowling ball on Earth due to air resistance, not because free fall physics differs for each.
  • Free fall is the vertical component of projectile motion: projectile motion combines free-fall vertical motion with independent constant horizontal motion.
  • Real falling objects eventually reach terminal velocity, once air resistance grows large enough to balance gravity — free fall describes the phase before that balance point.
  • The direction of "falling" doesn't have to be downward: the same equations apply to any object accelerating uniformly under a constant force, though gravity-driven vertical fall is the classic case.

Related Calculators

Free Fall Calculator →Calculate free fall time and final velocity from a drop height under gravity. Enter a height in meters to instantly get fall time and impact velocity, ignoring air resistance.
Projectile Motion Calculator →Calculate projectile motion instantly — enter initial velocity and launch angle to get max height, time of flight, and horizontal range, with a trajectory diagram.

Related Terms

Projectile MotionProjectile Motion (Physics)Terminal VelocityTerminal Velocity (Maximum Falling Speed)

Frequently Asked Questions

No — in true free fall (no air resistance), all objects fall at the same rate regardless of mass, since gravitational acceleration (g) is the same for every object at a given location. This was famously demonstrated by dropping a hammer and a feather simultaneously on the Moon, where there's no atmosphere to create air resistance, and both hit the ground at the same time.
On Earth, air resistance (not gravity) is responsible for the difference — a feather has a large surface area relative to its weight, so air resistance slows it dramatically, while a bowling ball's air resistance is negligible relative to its weight. Remove the air (as in a vacuum chamber) and both objects fall at exactly the same rate.
Standard free fall calculations use g = 9.8 m/s² (or 9.81 m/s² for more precision) on Earth's surface, though the exact value varies very slightly with altitude and latitude. The [Free Fall Calculator](/free-fall-calculator/) uses this standard value for its computations.
Free fall assumes no air resistance at all, so velocity keeps increasing indefinitely the longer an object falls. In reality, air resistance increases with speed until it balances gravity, at which point the object reaches a constant [terminal velocity](/glossary/terminal-velocity/) and stops accelerating — free fall is the idealized case before that balance point is reached.
Time to fall a distance d (starting from rest) is calculated as t = √(2d ÷ g). For example, falling 20 meters takes √(2×20÷9.8) ≈ 2.02 seconds, which the [Free Fall Calculator](/free-fall-calculator/) computes directly from any entered height.