# What is the speed of gravity 1

## Stratospheric jump How fast can a person fall from the sky?

### Record: 1,341.9 km / h

The record holder is the Austrian extreme athlete Felix Baumgartner. In October 2012 he reached a speed of 1,341.9 km / h in free fall, making him the only person to break the sound barrier.

### Gravitational force and air resistance

Two factors are decisive for the speed: the gravitational force of the earth and the air resistance. The gravitational pull has the same effect on everything that falls: A person is accelerated just as strongly as a falling leaf or a raindrop, namely with the so-called acceleration of gravity of 9.81 m / s².

That means: Without air resistance, we would be 9.81 m / s per second in free fall - that's the equivalent of 35 km / h - faster: after two seconds we fall at 70 km / h, after 3 seconds at 105 km / h and so on further. After a minute we would have a speed of 2,100 kilometers per hour - so we would have broken the sound barrier long ago.

The fact that it doesn't get that far is due to air resistance. This increases with the speed and at some point it balances out: Humans are then accelerated by the gravitational pull of the earth just as strongly as they are simultaneously slowed down again by air resistance. And then it doesn't get any faster.

### Parachutists reach about 200 km / h

With normal skydivers this happens after 6 to 7 seconds. A parachutist usually reaches a speed of around 200 km / h - and then hopefully the parachute will open at some point. However, skydivers have a special position. You spread out, fly lying on your stomach and stretch your arms and legs at an angle. That increases the air resistance.

If you instead jumped your feet down - like most people jump from a 5-meter board in the swimming pool - you can get a lot faster. And you get even more streamlined if you jump with your head down.

### How to break the sound barrier anyway

Baumgartner managed to break the sound barrier because he started from very high above. He rose in a helium balloon to a height of 39 km. So almost four times as high as a normal passenger plane.

At this altitude the air is so thin and therefore the air resistance is so low that it is hardly slowed down, at least for the first minute. That's why he broke the sound barrier after half a minute.

Of course, it's not that easy to jump down from such a height: Felix Baumgartner was wearing a pressure suit and had been preparing for the jump for years. Incidentally, he was advised by Joseph Kittinger. Kittinger was the last to have dared to do something similar before him. That was in 1960: Kittinger, a US fighter pilot and extreme balloon driver, jumped from a height of 30 kilometers and reached 988 km / h.