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Energy in Space

  • Thread starter Avis
  • Start date
  • #1
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Homework Statement



A 1250kg meteor rock fragment is momentarily at rest at an altitude of 3000km above the surface of Neptune. Neptune has a mass of 1.03x1026kg and a radius of 2.48x107m.

Determine: how much work is done on the rock by Neptunes Force of gravity as the rock falls to Neptunes surface (I got the answer to this one it was 3.74x1010J

I need help on: the velocity with which the rock strikes Neptunes surface

Not sure where to start with this one.
 

Answers and Replies

  • #2
32
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If you can find the gravity on Neptune, you can use conservation of energy to determine it's velocity.
 
  • #3
42
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so:
W=Ek
3.74x10^10j=1/2mv^2
3.74x10^10j=1/2(1250kg)v^2
v= (square root of) 3.74x10^10j/1250kg
= 7.7X10^4

But the answer says 7.7X10^3

Where did i go wrong?
 
  • #4
32
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The 1/2 magically disappeared. :) You just forgot to multiply by 2, but you got essentially.
 
  • #5
42
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i screwd up there... when i take half of the 1250kg i get the answer above.
 

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