I’m having some trouble wrapping my head around this concept. How does falling/reaching terminal velocity change depending on the force of gravity and atmosphere/drag. Example. Falling from the cliff on the Moon vs Earth or Mars vs. Earth.
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Terminal velocity is the maximum at which you can fall through a fluid (air, in the Earth’s case), regardless of gravity.
Since there’s no atmosphere on the Moon you would continue to accelerate until you landed on the surface.
Uranus has a tiny moon called Miranda, which has the tallest known cliff in the solar system at 20km high. Gravity is tiny (1/128 that of Earth) so it would take you 12 minutes to fall off it, but there’s no atmosphere, so no terminal velocity, and you accelerate all the way down.
Terminal velocity is the speed at which the force of gravity pulling down on you is the same as the force of air resistance pushing back as you fall.
On the moon, though gravity is lower, there’s no air resistance to slow you down, so terminal velocity is infinite. If the moon had the same atmosphere as Earth, terminal velocity would be lower.
This is primarily a function of density. It might actually be easier for you to think of terminal velocity as buoyancy. The other important component is atmospheric density. There’s also your mass and profile, but we’ll assume that they are the same in all cases and the difference is negligible. Your cliff example is ok, but lets use the real life one, which is a space shuttle entering atmosphere.
Since the Moon has no real atmosphere, there’s pretty much no terminal velocity. Or if there were, it would be something nonsensical, like 10% the speed of light, or at the least fast enough so if you were traveling at terminal velocity on the moon, you would either hit it or you would orbit the sun.
There’s no good way to aerobreak on the moon since you’re lacking the aero part.
Mars has some applicable atmosphere. Terminal velocity on mars would be much higher than on earth due to its thinner atmosphere, but it’s at least worth considering. If you do it right, you can slow down to near terminal velocity on mars and save your parachutes some stress. If you managed to jump from a high enough cliff on mars, your terminal velocity would be about 10-100x higher than earth, since the atmospheric pressure is so much lower.
The real interesting question is a gas giant like Jupiter. Jupiter is large enough to have a terminal velocity ‘profile’. If you started, say, 1000 KM above the ‘surface’ of Jupiter you would accelerate to a very high terminal velocity, probably something like 1000-10000x the terminal velocity of earth, then slowly slow down as the density increased. Assuming you could somehow survive, you would eventually reach a point where your density would be less or equal to than that of Jupiter and your terminal velocity would be zero. You would be forever stuck floating in a high pressure hydrogen soup with a density equal to yours.
Terminal velocity is only affected by drag. Differences in surface gravity between planets will only affect acceleration, meaning that it might take more or less time for a falling object to reach terminal velocity, but the final speed will still be the same.
In a vacuum, where there is no drag, there is no terminal velocity other than the speed of light.
Terminal velocity is not affected by gravity. In a lower-gravity environment it may take you longer to reach terminal velocity, but assuming the atmosphere is similar to Earth’s, your terminal velocity will be about the same. If the atmosphere changes, *then* your terminal velocity changes.
The Moon is a bit of an odd case, because there is no atmosphere to speak of. Without an atmosphere, there can be no terminal velocity, at least not in the sense we usually think of it. You’re still limited by *c*, but that’s not the same thing, and it is very unlikely that you would fall long enough to reach *c* anyway.
Terminal velocity is a balance of two forces: gravity and drag. Drag increases with speed and depends on the density of the atmosphere and the shape of the falling object. Gravity, in this context, can be considered constant.
On the moon, there’s negligible atmosphere, which means pretty much no drag, and therefore no terminal velocity: something falling on the moon will just keep accelerating until it hits something.
On Mars the atmosphere is very thin, so terminal velocity is higher than on earth, even though the gravity is also lower.
If you had a planet with Earth’s atmosphere and lower gravity, the terminal velocity would be lower.
Less gravity – get to terminal velocity slower. Velocity will be lower also because force is lower.
Less drag (less air) – higher terminal velocity due to hitting fewer air molecules
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