Earth impact velocities.

[sstein]

Hello,

I'm sure someone will be able to explain this to me. If an object orbiting the sun hits the earth the maximum speed it can be travelling is 72km/s. How do you work this out, and why is something travelling quicker than 72km/s not able to hit the earth.


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Stuart

Edited: Original Post, stupidly, had the maximum as 72m/s, when it should have been KM/S. Sorry...

Question still stands though, if anyone has the definitive answer.

Edited by sstein on Sunday 31st August 23:49

[marshalla]

no discussion of orbital velocity until you apologise to the rest of us for letting Gordon Brown out.

[mybrainhurts]

Don't worry, Brunstrom will put a stop to that...

[sstein]

I had the shot! I promise I did, but the high-ups never gave the green light. No green light and I don't pull the trigger...




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Stuart

[grumbledoak]

I've not read that anywhere, and I've no obvious reason to believe it to be true.

[Eric Mc]

Is that because anything travelling faster wouldn't actually be orbiting the sun in the sense that maybe 72m/s is the fastest an object can be in a captive orbit around the sun. Anything faster and it would escape the sun's gravitational pull and leave the solar system.

In actual fact, I am pretty sure higher impact speeds could be achieved by an object orbiting the sun and hitting the earth. What about the case where the object is orbiting the sun in a retrograde direction and therefore more or less hits the earth virtually head-on.

It would be interesting to know the figures.

[ypauly]

sstein said:

Hello,

I'm sure someone will be able to explain this to me. If an object orbiting the sun hits the earth the maximum speed it can be travelling is 72m/s. How do you work this out, and why is something travelling quicker than 72m/s not able to hit the earth.


-

Stuart

I'm no scientists
but this is fairy easy, it would start to go into a straight line as the gravity of the sun cannot hold it in orbit any longer.
Imagine you are on a childs roundabout the faster it goes the harder it is to stay on, as the centrifugal (spelling i know) force wants to throw you off.

[TheEnd]

it's probably due to the escape velocities, ie something orbiting the sun faster than 72m/s will shoot off into space?

[hairykrishna]

sstein said:

If an object orbiting the sun hits the earth the maximum speed it can be travelling is 72m/s.

I think you may have the wrong end of the stick somewhere - this statement doesn't really make sense. 72m/s relative to what?

[sstein]

Thanks ypauly That is probably it.

site said:

The minimum impact velocity on Earth is 11 km/s. Typical impact velocities are 17 km/s for asteroids and 51 km/s for comets. The maximum Earth impact velocity for objects orbiting the sun is 72 km/s.

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Stuart

[odyssey2200]

hairykrishna said:

sstein said:

If an object orbiting the sun hits the earth the maximum speed it can be travelling is 72m/s.

I think you may have the wrong end of the stick somewhere - this statement doesn't really make sense. 72m/s relative to what?

relative to the plane on the conveyor belt!

[HarryW]

hairykrishna said:

sstein said:

If an object orbiting the sun hits the earth the maximum speed it can be travelling is 72m/s.

I think you may have the wrong end of the stick somewhere - this statement doesn't really make sense. 72m/s relative to what?

metres travelled over a 1 second period, why

[DieselJohn]

Sounds like nonsense to me, the earth is travelling a lot faster than that (relative to the sun for the sake of arguement). If it was to hit another earth orbiting in the oposite direction at the same speed, bosh.

[odyssey2200]

http://uk.youtube.com/watch?v=lpbjXFS8Zag

Just remember that your standing on a planet thats revolving....

[elster]

72KM/s sounds a bit more reasonable.

[hairykrishna]

The various people suggesting that this has some relation to the suns escape velocity are working on the wrong order of magnitude. Bear in mind that the escape velocity for earth (relative to earth) is ~11 kilometers per second.

[sstein]

yahoo said:

"Earth orbital speed is 28.8km/s, orbital escape speed is the square root of two times this, 42.1km/s, and surface escape speed is 11.2km/s. The slowest meteor would be one that just catches up with the earth then "falls", 11.2 km/s. Don't expect anything less than 12km/s. But a retrograde body in parabolic orbit (the maximum speed for a body at a distance of 1AU that is a member of the solar system) might close with earth at a speed of 42.1+28.8=70.9km/s plus the 11.2 "fall" for a total of (total2=70.92+11.22) 72km/s. So we expect a range of 12-70km/s

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Stuart

Edited by sstein on Sunday 31st August 23:52

[TimJMS]

sstein said:

72m/s

elster said:

72KM/s sounds a bit more reasonable.

In for teh win here :

So slow. My mother can get to Mac Donalds quicker that from a standing start when I tell her to in the Micra. If the Chixculub comet had hit at that speed all the flora, never mind the fauna would have had time to run away first.

Ergo the proposition is wrong. What are we going to be gently bumped to death?

What a load of effluvium.

HTH

[grumbledoak]

72km/s sounds better. The voyager probes were doing over 15km/s as they left the solar system. Though in truth I'm still not sure I can see why there would be an upper limit at all. Isn't the speed of light 300,000km/s ?

[TimJMS]

I see the proposed speed has now been amended.

Mother will need the Micra turbocharging.