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
Terminal velocity is reached by two opposing forces in balance: gravity and air friction.
Air friction is proportional to air density and speed squared.
Air density reduces with altitude all the way ro zero.
There is no terminal velocity in space except the speed of light for totally different reasons.
So if you drop your object from high enough, it can achieve much higher speeds and as air density rises, friction does too and the terminal velocity decreases.
So, something that burns up in the atmosphere is coming from a place without terminal velocity into one that does, so must slow down, and any slowing down based on friction exchanges speed for heat.
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