Escape velocity

[Epidemic]

Ok all you big brained techimo types.

Why is there an escape velocity. Is that based on our fuels or something else?

Simply put. If I had a ship that traveled 100 MPH and traveled for 10 days would I escape earths gravity at 24000 miles. Or carry it out further perhaps 1000 days at 2,400,000.

What ever time frame you suggest. I alway hear that you need to reach escape velocity and it makes no sense to me except in the case where fuel/energy is limited.

[TheBurningCat]

i think escape volicity is like 11km/sec.

If i remmeber correctly.

Tell you the truth i'm not sure what your question is

[Epidemic]

The question is.

If I travel below escape velocity for a long enough time will I escape the earths gravity.

Eventually I will be so far away from earth that two mph will keep me going for ever.

I knew nothing about Escape Velocity til I did some searching for an answer. Now I know a little less than nothing about it

Defined:
escape velocity
Astronomy
• the velocity that an object needs to reach parabolic or hyperbolic orbit around its primary, which permits it to escape to infinity.

Escape of an Atmosphere


*fixed link

Interesting question.

Based on all the things I just thought about, my answer is no.

[RedFury]

Without looking for the scientific answer and flexing my minuscule brain muscle I think of it like this:

Escape velocity is the speed you need to obtain ( minimum ) in order to break the grip gravity has on the object being accelerated.

Think of it this way. Lets say you have a rocket that can propel a car to 300mph. You are running across the surface. Stand that same car up and point it to space. If the rocket can't actually lift the car, you're stuck on earth. You may have been able to obtain the speed necessary to escape the earth's gravitational pull, but you aren't actually escaping earth.

It's easier to slide two magnets across each other than pull them apart. Takes more energy to seperate the magnets. I'm already seeing that I'm not exactly answering the question, but this is my take on the direction of the thread.

You could also look at the satellite game posted and get a visual idea of escape velocity. As the satellites get close to earth, they speed up and sling shot off into a larger orbit. Being as they aren't self propelled, they slow down and get captured by the earths gravity. If you were to sling shot around earth like that and keep that speed going, you would continue off into the void.

[CERuppel]

Escape velocity and escaping the gravity well are two diferent things.

Escape velocity (simple) is the speed at which you will not fall back to the ground. It is the speed a satilite needs to achieve orbit around the earth (earths escape velocity).

Escaping the gravity well is another matter. Yes you could escape the gravity well if you could just keep going at a constant rate for long enough... But each second you are going you have to expend 'x' amount of energy just to overcome gravity, and then 'y' amount of energy to go forward. Most rockets don't have the fuel for this (outside of sci-fi). So the use of 'sling shot' orbits comes into play. That is where you start in orbit, decelerate so you fall toward the planet, and then accelerate at the closest approach. This results in much higher (MUCH) speeds than just accelerating from orbit.

Why? I half remember this from high school, but probably got some of this wrong. Orbit (for this explaination) is the stable orbit around a planet. Orbit is a tricky thing, the closer orbits are shorter, and the farther orbits are longer. But they all have the same speed. If you are at 100miles or 500 miles it does not matter, the speed youare traveling at is the same. However your relative speed to the planets surface changes. An orbit that is 100 miles out (from plnets center) is some 320 miles in diamiter. An orbit that is 500 miles out is some 1600 miles in diamiter. Butyouare going at the same forward speed so the closer orbit only takes (for example) 3 hours, while the further orbit takes 16 hours.

Now for the funny stuff. In order to change orbits you have to accelerate to go out (into a slower orbit) and decelerate to fall into a faster orbit. You would also have to correct your speed to re-stabilize your orbit after you fell/rose to the desired orbit.

However, since while in the process of changing orbits you are not stable it is possible to decelerate, sling shot around the planet (like a comet around the sun) and end up in a higher orbit. This is how the Apollo moon rockets got from orbit to the moon. And it is how our probes get to the other planets of this solar system.

There, did I confuse you enough for one morning?

(Hope I got that right, or one of my teachers will be by to pound some sense into me).

Hey Epidemic, now that you know where you plan to go in that laser-gravity ship projectile of yours?

[Creatures]

the answer is already given,
but i explain it like this,

you need a force (escpape velocity), which is bigger than the Gravity (G-force)!

Creatures

[Theophylact]

Look at it this way: escape velocity is the velocity an object dropped from an infinite height would have when it finally hit the surface of the earth. The velocity at which you fire something upward (in the absence of air resistance) is the same as it will have when it comes back down. (That's why so many people are killed by shots fired into the air in celebration.)

So escape velocity is the velocity you have to impart to an object for it to be able to escape to a theoretically infinite distance. Not the same as orbital velocity; that's quite a bit less -- unless the orbit is infinitely high.

You never "escape" the gravity well, because the force of gravity diminishes as the inverse square of the distance; ten times the distance, one hundredth the attraction; a million times the distance, a quadrillionth the attraction, and so on. The force is still attracting at infinite distance. But it gets very weak.

By the way: if the force of gravity is so great that escape velocity is more than the speed of light, you have a black hole.