What is the terminal velocity of an object falling towards earth assuming no air resistance

[MAME]

People can fall around 250 mph while skydiving if they become as aerodynamic as possible.

Assuming no other forces are acting on the falling object, that is they're falling in a vacuum, how fast will the terminal velocity be?

It was suggested that an object falling towards Earth in a vacuum will infinitely accelerate, but I believe it will hit a very finite speed that is solely dependent on the gravitational pull of Earth.

 

[chuckywang]

Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

 

[MAME]

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

 

[ViRGE]

Originally posted by: MAME

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

Relativity. Basically they'd accelerate towards c in an asymptote fashion, never reaching it.

 

[flxnimprtmscl]

There is no such thing as terminal velocity for an object falling in a vacuum.

 

[Ballatician]

i concur

 

[jagec]

Originally posted by: MAME

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

Generally hitting the surface of the planet to which you are accelerating tends to slow you down a bit.

 

[JRich]

Originally posted by: jagec

Originally posted by: MAME

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

Generally hitting the surface of the planet to which you are accelerating tends to slow you down a bit.

:laugh:

 

[gooseman]

Would it not be 9.8 meters/second squared?

 

[fallensight]

Originally posted by: gooseman
Would it not be 9.8 meters/second squared?

that is the acceleration of the falling object, not the terminal velocity.

 

[dug777]

It won't take off

 

[RedCOMET]

law of the conversation of energy great in an ideal situation such as an object falling towards the earth with no wind resistance. mgh = 1/2mv^2


Hooray Scicence, bitches

 

[Paperdoc]

Originally posted by: MAME

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

It could take a while. At earth's surface, the force of gravity produces an acceleration rate of 9.8 m/s per second. Round that off to 10. Now the speed of light of 3.0 x 10^8 m/s So to reach that speed, you would have to undergo that acceleration rate for about 30 million seconds, or close to a year. I have not calculated how far you would travel in that time, but it certainly means you'd have to start out VERY far from earth. Of course, in that situation you would not be close enough to the earth to experience the same gravitational pull, and the math gets more complicated. To work that out, it would be easier to reconsider the problem as a body in space being pulled into our sun, say, from among the planets.

 

[Albatross]

Originally posted by: dug777
It won't take off

0.9999=1? :shocked:

 

[cKGunslinger]

Did you know that the terminal velocity of cats is a non-lethal speed? Technically, you can toss a cat from an airplane and it will live.

 

[destrekor]

well, consider that Earth's terminal velocity is somewhere around 700-750mph iirc, we did the calculations in a class once. However, yea, no air resistance should theoretically provide no limit to the ultimate speed, but gravity means you are falling towards something.. so, you'll hit that object before ever reaching any insane speeds. a black hole at the event horizon may provide the speeds one would enjoy though.

 

[jiggahertz]

Originally posted by: RedCOMET
law of the conversation of energy great in an ideal situation such as an object falling towards the earth with no wind resistance. mgh = 1/2mv^2


Hooray Scicence, bitches

I must have missed that law of conversation.

 

[overst33r]

I thought terminal velocity for a human was like 140mph?

 

[johnjbruin]

If there is no friction, and there is infinite distance to fall so you can keep accelerating, you probably get a black hole, where even light can't escape. Dunno... just guessing.

 

[jiggahertz]

Originally posted by: Paperdoc

Originally posted by: MAME

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

It could take a while. At earth's surface, the force of gravity produces an acceleration rate of 9.8 m/s per second. Round that off to 10. Now the speed of light of 3.0 x 10^8 m/s So to reach that speed, you would have to undergo that acceleration rate for about 30 million seconds, or close to a year. I have not calculated how far you would travel in that time, but it certainly means you'd have to start out VERY far from earth. Of course, in that situation you would not be close enough to the earth to experience the same gravitational pull, and the math gets more complicated. To work that out, it would be easier to reconsider the problem as a body in space being pulled into our sun, say, from among the planets.

The gravitational force also falls off as a function of distance squared. So when you go out to 10^12 km or whatever distance you would need, the object would not be accelerating at 9.8 m/s^2.

 

[DrPizza]

Didn't see it mentioned, but for what it's worth, if the object came from the surface of the earth, (something thrown upward), the terminal velocity will be equal to the launch velocity. A better way to say it than terminal velocity is "the velocity it achieves at the moment just before impact."

If the object comes from space, then there is a minimum velocity at which it will reach the surface of the earth: equal to the escape velocity (Wikipedia link: here). About 11.2 kilometers per second.

Now, if it's a powered object (Rocket, UFO, etc.) then any velocity is possible (obviously.)

 

[2Xtreme21]

Originally posted by: jiggahertz

Originally posted by: Paperdoc

Originally posted by: MAME

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

It could take a while. At earth's surface, the force of gravity produces an acceleration rate of 9.8 m/s per second. Round that off to 10. Now the speed of light of 3.0 x 10^8 m/s So to reach that speed, you would have to undergo that acceleration rate for about 30 million seconds, or close to a year. I have not calculated how far you would travel in that time, but it certainly means you'd have to start out VERY far from earth. Of course, in that situation you would not be close enough to the earth to experience the same gravitational pull, and the math gets more complicated. To work that out, it would be easier to reconsider the problem as a body in space being pulled into our sun, say, from among the planets.

The gravitational force also falls off as a function of distance squared. So when you go out to 10^12 km or whatever distance you would need, the object would not be accelerating at 9.8 m/s^2.

Wouldn't you still be going at the same speed, but distance and time would begin to stretch?

 

[jiggahertz]

Originally posted by: 2Xtreme21

Originally posted by: jiggahertz

Originally posted by: Paperdoc

Originally posted by: MAME

Originally posted by: chuckywang
Terminal velocity exists when the force of the air resistance equals the force of gravity on the object. If there is no force of air resistance, then what will counteract that gravitational force?

apparently nothing, I found something saying that objects will accelerate indefinitely.

However, what's to stop an object from surpassing the speed of light given this vacuum scenario?

It could take a while. At earth's surface, the force of gravity produces an acceleration rate of 9.8 m/s per second. Round that off to 10. Now the speed of light of 3.0 x 10^8 m/s So to reach that speed, you would have to undergo that acceleration rate for about 30 million seconds, or close to a year. I have not calculated how far you would travel in that time, but it certainly means you'd have to start out VERY far from earth. Of course, in that situation you would not be close enough to the earth to experience the same gravitational pull, and the math gets more complicated. To work that out, it would be easier to reconsider the problem as a body in space being pulled into our sun, say, from among the planets.

The gravitational force also falls off as a function of distance squared. So when you go out to 10^12 km or whatever distance you would need, the object would not be accelerating at 9.8 m/s^2.

Wouldn't you still be going at the same speed, but distance and time would begin to stretch?

I'm not sure what you mean by distance and time would begin to stretch. If you are significantly farther from the earth the gravitational force is smaller, so an object would not be accelerating at 9.8m/s^2. Or to put it another way, acceleration is a function of distance from the earth.

 

[shortylickens]

Originally posted by: mariok2006
I thought terminal velocity for a human was like 140mph?

Thats what I heard from a lot of parachute riggers in the Navy.

As for the OP's question: It depends on the density of the object. A feather probably wont fall at 140mph no matter how high you drop it. (Unless it were wet, and then its density would be much higher.)

Aerodynamics plays a big role too. If its dense but has the right shape it could still fall slowly.

OH CRAP! I need to learn how to read english!
If theres no air there is no terminal velocity. That whole concept is based in the condition the moving object presses against the air and the air eventually builds up enough opposition it is equal in WEIGHT (not mass) to the falling object. When you have two equal forces acting on each other, neither one can ACCELERATE (change velocity) which means whatever speed your rock or ball or human was traveling at, thats its set speed and it wont increase or decrease anymore. TERMINAL means final. Its final velocity.

EDIT:
Also as far as the infinite acceleration goes, you need insane amounts of energy to accelerate anything to the speed of light, gravity would probably never be enough. No matter how strong it was and how far away to object started, it would collide with the source of gravity long before it hit lightspeed. But in theory, yes, it would keep accelerating because the gravity is a constant force. And as long as you can constantly apply a force you can constantly increase (or change) velocity.

 

[BriGy86]

didn't they do studies on the moon where they dropped a hammer and a feather and they fell at the same rate?

I believe the moon is technically a vacuum since there is no atmosphere.