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Quick question about Escape velocity 
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#1
Nov2909, 09:31 PM

P: 239

Okay this equation is giving me some trouble, I just have a question
vescape = √(2GM)/R Say I wanted to find the escape velocity of myself 3 meters away So I would use vescape = √(2)(6.674*10^11)((145*4.44)/9.8)/(3) = 5.419003598 *10^5 So does this mean something that moves that slow cannot escape me farther than 3 meters away? It doesn't seem right. My gravitational field feels so ephemeral. Is this correct? 


#2
Nov2909, 11:28 PM

HW Helper
P: 2,323

I don't know why your mass is 145/9.8 (you weigh only 15 kg???), but yes, your escape velocity is tiny, and yes, something moving slower than your escape velocity can't escape from you in an ideal world. In the real world, turbulence, Brownian motion, and the gravity of other objects make that conclusion moot.



#3
Nov3009, 04:09 PM

P: 239

Weight is a force.
F = MA Therefore M = F/A or F/G So I could take my weight in ibs and divide it by 9.8 to get my mass. 


#4
Nov3009, 04:21 PM

Mentor
P: 41,325

Quick question about Escape velocity
If you weigh 145 pounds, your mass is about 66 kg. 


#5
Nov3009, 04:26 PM

P: 239




#6
Nov3009, 04:40 PM

P: 279

In theory, if you were isolated in a big region of empty space, and tried to toss say a marble away, it would return to you if the initial velocity were less than escape velocity, or it would go into orbit around you if it had a correct satellite velocity. I think ...
http://en.wikipedia.org/wiki/Escape_velocity The proper unit for mass in British enegineering is slugs, that is, your weight in pounds force divided by standard gravity 32.174 ft/s/s. Always work in some consistent set of units. 


#7
Nov3009, 04:49 PM

Mentor
P: 41,325

Of course, this calculation assumes that you are a spherical ball! (That's how the escape velocity formula is derived.) So I wouldn't take it too seriously. 


#8
Nov3009, 05:00 PM

P: 239

Thanks, the weight thing in newtons messed me up. Thank you so much anyways. I understand now. 


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