Calculating Velocity of Meteor Rock Fragment Falling on Neptune

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Homework Help Overview

The discussion revolves around calculating the velocity of a meteor rock fragment falling to the surface of Neptune. The problem involves gravitational forces and energy conservation principles, with specific values provided for the mass of the meteor and Neptune, as well as the initial altitude of the fragment.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss using conservation of energy to relate work done by gravity to the kinetic energy of the falling rock. There are attempts to derive the velocity from the work-energy principle, with some questioning the calculations and assumptions made in the process.

Discussion Status

Participants are actively engaging with the problem, with one suggesting a method based on conservation of energy. There is a recognition of a calculation error by one participant, prompting further exploration of the correct approach to find the velocity.

Contextual Notes

There is a mention of a discrepancy in the calculated velocity, indicating potential confusion regarding the application of the work-energy theorem. The original poster expresses uncertainty about where to start, highlighting the challenge of applying theoretical concepts to the problem.

Avis
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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.
 
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If you can find the gravity on Neptune, you can use conservation of energy to determine it's velocity.
 
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?
 
The 1/2 magically disappeared. :) You just forgot to multiply by 2, but you got essentially.
 
i screwd up there... when i take half of the 1250kg i get the answer above.
 

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