So, to my knowledge, things burn up when entering the atmosphere due to the friction caused by all of the air molecules hitting them on the way down which would make sense when an object gets faster, it hits more air molecules, and heats up, however, when an object reaches terminal velocity it no longer goes any faster, and objects that aren’t aerodynamic have a relatively low terminal velocity, meaning it may go just as fast being dropped from a tall building, and obviously, things don’t burn up (or even get hot) when being dropped from a tall building. So my question is why exactly being something falling into the atmosphere will burn up, but not if it’s dropped at a much lower height that would still reach it’s terminal velocity.
In: Physics
Both dropped things and things falling into the atmoshere reach terminal velocity, the difference is that dropped things start from zero, and their speed goes up, until it reaches terminal velocity. Things falling into the atmosphere typically go much faster than their terminal velocity, and need to *slow down* in order to reach it. And things that go fast have a lot of kinetic energy, which will get converted to heat as they slow down to their terminal velocity.
It’s because objects re-entering the atmosphere from orbit are already going much, much faster than terminal velocity.
If an object was somehow completely stationary relative to the earth and started to fall into the atmosphere, then it would not get that fast, and it would not burn up. Objects in low earth orbit are going at around 17,000 mph while they are in the vacuum of space.
So why don’t they just burn their rockets to slow down, and then enter the atmosphere? Because the amount of full needed would be huge – roughly the same amount that was needed to send it up there in the first place. So they use the air to slow down.
If your car is going 60mph and you hit a block of jell-o in the road your car is still going to crash before going through it.
An object entering the atmosphere is going faster than terminal velocity and the atmosphere is trying to slow it down to that speed, the friction between the air and the object is what causes the burning.
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