# Questions tagged [escape-velocity]

The velocity an object must travel to successfully exit the gravitational influence of a body.

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The escape velocity from a common gravtational attractor means that a body lounched away from the attractor will never turn back. But in the case of a BH at the event horizon this escape velocity is $... • 2,105 0 votes 3 answers 79 views ### Why we say that total energy should be zero at infinity in the derivation of escape velocity? I am little confuse about escape velocity. I have been taught that potential energy is arbitrary and hence we always assume it zero at infinity but actually it can or cannot be zero. My question is ... • 111 0 votes 4 answers 58 views ### Is a planet's escape speed the same speed as in a circular orbit around it? I had this intuitive idea. An object shot upwards with the escape velocity must have the same velocity as the object has when it's in circular orbit at the same height as from where shot upwards ... 12 votes 2 answers 2k views ### If the escape velocity at the event horizon is the speed of light does it mean that slower bodies won't move away at all? If we say that the escape velocity from a planet is say 10 km/s we think that a slower body will move away from that planet but will be eventually forced to fall back on the planet. In simple words we ... • 2,105 0 votes 1 answer 58 views ### Maximum height reached by an object Here, in the last line, from the formula s is negative, but how can s be negative? Also, should it not be s=u^2/2g instead of s= - u^2/2g? • 13 0 votes 4 answers 116 views ### Have solar wind particles escaped the Sun's gravity or will they eventually return back? I've read that solar wind consists of hydrogen atoms that are, near the Earth, travelling at about 450 km/s. This is only 3/4 of the Sun's escape velocity, but then the Earth is also 150 million km ... • 305 0 votes 0 answers 19 views ### Is the speed of ejected particles proportional to the mass of the supernova star? Is the speed of ejected particles proportional to the mass of the supernova star? Has the nuclear explosion more power if the supernova object has more mass? In simple words is it true that there is ... • 2,105 1 vote 0 answers 40 views ### Why is the escape "energy"$e=1$for a massive object in Schwarzschild metric? Being$e$the quantity found through Killing vector$(-1,0,0,0)$, $$e = (-1,0,0,0)\,\cdot\,(\dot{t},\dot{r},\dot{\theta},\dot{\phi})$$ For the Schwarzschild metric,$$e = \left(1 - \frac{2M}{R}\right)\... 0 votes 1 answer 59 views ### When is a moving test mass unbound from a black hole? Imagine a small test mass$m$with speed$v$and distance$r$from a Schwarzschild black hole of mass$M$. (The test mass is anywhere, but NOT on the horizon. Also,$m << M$.) What condition on$... 2k views

### Why does the value of the escape velocity approach 0?

I am a little confused about escape velocity. Does the escape velocity always approach 0 as we go to an infinitely far distance even if there isn't any friction? If so, why does it approach 0? Shouldn'...
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### Would a projectile launched with the escape velocity reach a final velocity of 0 as time approached infinity?

I just wanted to check my understanding of escape velocity. If a projectile was to launch and have the exact velocity as the escape velocity of the earth, it would have a final velocity of 0 correct? ...
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### Escape velocity at an angle near a black hole

What's the formula for the velocity required to escape at an angle (not normal) near a black hole? I know for example that the required velocity not to impact the black hole at $90$ degrees is larger ...
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### Escape velocity at 45 degrees near a black hole [duplicate]

what if the formula for the escape velocity at 45 degrees compared to 90 degrees when you are near enough to a black hole for relativistic effects to become significant? I know that near enough to the ...
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### What happens if a projectile is projected with escape velocity but not upwards?

This may be a dumb question, however I was confused with escape velocity and in the end determined that escape velocity is based off of energy, whereby (i think assuming air resistance and all that is ...
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### $G$ expressed as a function of $c$?

The escape velocity for a given mass $M$ and a given radius $r$ is given by: $v_e = \sqrt{ \frac{2 G M}{r} }$ With $M$ = 25 kg and $r$ = 1/$c$ we have: $v_e = 1.0001917061 \approx 1$ Can we express $G$...
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### Lift (elevator) and equivalence principle

A famous example to explain the equivalence principle is a lift (elevator) in the space (no gravity field), moving up with the acceleration of "g". It is said there is no way (experiment) ...
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### Deriving a function of $r$ (distance from the planet's center) for velocity for a projectile launched beyond escape velocity

This is my first post here, and I'm here because I'm rather confused. I'm doing some homework at the moment and the question is asking for a function $v(r)$ which represents the velocity of a ...
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### Can special relativity contain general relativity?

I realized that considering merely an upper limit for speed per se can hint at gravity(more precisely black holes). Very naively with Newtonian mechanics, one can derive the following formula for ...
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### Can you jump off the counterweight of a space elevator at 1.2 x geostationary orbit? Is the assumption correct that an 80 kg person would weigh 2 kg?

Edit: This very silly question was answered in the comment by @pm-2ring - it's an orbit, you're weightless Can you jump off the counterweight of a space elevator (https://en.wikipedia.org/wiki/...
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### Minimum mass of asteroid that could knock moon away [closed]

What is theoretically the minimum mass of asteroid, coming from deep space, that could knock the Moon away from Earth? The asteroid is not hitting the Moon, just interacting with it by gravity. I was ...
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### Can you exit the event horizon with a rocket?

The reason given in most places about why one cannot escape out from an event horizon is the fact that the escape velocity at the event horizon is equal to the speed of light, and no one can go faster ...
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### Question regarding Kleppner Kolenkow Example 5.5 "Escape Velocity—the General Case"

In example 5.5 from Kleppner Kolenkow (2nd edition), the general case of finding the escape velocity of a mass $m$ projected from the earth at an angle $\alpha$ with the vertical, neglecting air ...
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### May a star explosion be in that way weak that the expelled material gradually recollapse and form the star again?

May a star explosion be in that way weak that the expelled material gradually recollapse and form the star again? My question is not about would that explosion leave a neutron star as a remnant but ...
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### Black holes are not infinitely dense [closed]

If a black hole is infinitely dense, then therefore its terminal velocity in a determined field of gravity would be greater than the speed of light which is impossible, therefore a blackhole is not ...
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### What would be the event horizon for charge?

If there was a sufficient charge density, would it be possible for that charge to have an event horizon, a radius at which a charged particle would need to be going faster than the speed of light to ...
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### Would an anisotropic speed of light possibly allow light to escape a black hole?

It has been proposed that light coming toward the earth is near infinite but that light outgoing is near 1/2 c. I know we cannot directly measure the one-way speed of light, but if anisotropy were ...
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### Escape velocity questions

This topic really screwed with my head in school and my teacher could never answer my questions so I thought I would ask here. I will break it down with mathematics and then logic. Let's assume we ...
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### Escape velocity and Conservation of energy

If a physical body leaves earth with 11.2 km/s escape velocity with a certain amount of Mechanical energy, then how can it be said that the body will have 0 Mechanical energy at a point at infinity ...
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### What equation can I use to calculate escape velocity as the radius increases from the Schwarzschild radius? [duplicate]

At the Schwarzschild radius, the escape velocity is the speed of light for all objects. However, I'm looking for an equation that will calculate the escape velocity as the radius of the object ...
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### What is angle of escape velocity? [duplicate]

We know if a object has escape velocity (EV) it reaches space (ignore atmosphere friction), but at what angle. if an object travels parallel to earth surface with EV, will it escape curvature and ...