How fast can something fall?

This optional article explores how release height and air resistance affect a fall. It builds on the main lessons and does not introduce another definition of gravity.

Falling without air

Near Earth’s surface, a freely falling object gains about 9.8 metres per second of downward speed each second. Over a short drop, treating that acceleration as constant works well.

Farther from Earth, gravity is weaker. Moving the release point higher still increases the arrival speed, but the increase becomes smaller as the starting point gets farther away.

Imagine an Earth with no rotation or atmosphere, and ignore the gravity of other bodies. Release an object from rest. As you move its starting point farther out, its speed on reaching the surface approaches 11.2 kilometres per second.

This is Earth’s surface escape speed in reverse. It is not a universal maximum: an object arriving with additional initial speed can reach the surface faster.

Falling through air

As an object speeds up through air, the air generally pushes back harder. If the surrounding conditions stay steady, it can reach a speed at which drag balances its weight. It then stops gaining speed. This is its terminal speed.

There is no single terminal speed for every person or object. It depends on mass, shape, orientation and the surrounding air. The model’s human-shaped body approaches roughly 57 metres per second near the ground.

Higher in the atmosphere, thinner air allows much greater speeds. As the object descends into denser air, drag can slow it substantially.

Exploring different release heights

Felix Baumgartner’s 2012 jump provides one real comparison: he stepped from a balloon at roughly 39 kilometres and reached about 377 metres per second before slowing in denser air and later opening his parachute.

The model’s air-resistance setting was adjusted to reproduce that peak approximately. This gives it a real jump to compare with. Much higher releases take it well beyond that comparison.

Try a few high release points. The greatest speed during the fall changes considerably, while the speed near the ground becomes similar as the denser air slows the modelled body. A different shape or mass would give different results.

At extreme speeds, a real object would also heat up, lose material or break apart. This model keeps the body intact and its shape unchanged, even while slowing it very sharply. Those settings show what the simplified calculation produces, rather than a descent a person could survive.