ChatterBank0 min ago
terminal velocity
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i always understod that falling objects reach a terminal velocity, is this correct ?
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No best answer has yet been selected by druiaghtagh. Once a best answer has been selected, it will be shown here.
For more on marking an answer as the "Best Answer", please visit our FAQ.It is true in an atmosphere. Eventually you will reach a velocity where you cannot overcome air resistence. So a piece of paper will have a terminal velocity of naff all, whereas a bowling ball will be a lot faster. Also, at height, where the air is thinner, the velocity will be greater. It then follows that if you are in a vacuum(space), you will continue to accelerate as long as you are acted on by an outside force (eg gravity). However, you then start entering the realms of relativity, which says you cannot go faster than the speed of light, so you must reach a sort of terminal velocity, but I was never that good at A level physics, so I'll quit while I'm ahead!
sddsddean: Indeed, as an object's speed increases so does it's mass. Now since f=ma (Newton), to maintain a constant acceleration on that object, you'd need an ever increasing force in correlation with its ever increasing mass. Note that the objects velocity doesn't decrease, but rather the rate at which its speed increases does.
With respect to the original question sddsddean is bang on. Terminal Velocity is achieved when drag forces equal accelerative forces (Eg. gravity).
With respect to the original question sddsddean is bang on. Terminal Velocity is achieved when drag forces equal accelerative forces (Eg. gravity).
Well, this may be another of those questions where I'm wrong, but I'm sure I was taught at school that falling objects increase in speed initially but eventually (if they fall for long enough) they get to a point where they fall at a constant speed.
I'm sorry I can't give a reason why exactly but it was something to do with the formula and gravity becoming equal to each other or something.
gazzawazza: you're almost there. just substitute "the resistive force" (i.e. air resistance) for "the formula"(?!) and you're spot on. When the two forces (air resistance and gravity) acting (in opposite directions) on the object balance, the resultant force F = zero and therefore according to F = ma acceleration is also zero (i.e. constant, or 'terminal', velocity). Whichever correspondent said that mass increases with speed is wrong.