How Much Would You Weigh on a Smaller Planet?

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Homework Help Overview

The discussion revolves around a physics problem involving gravitational force and weight on a hypothetical planet with a mass and radius different from Earth. The original poster seeks to determine how much a person weighing 150 lb on Earth would weigh on this smaller planet.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the gravitational formula g=GM/r^2 and the implications of the mass and radius ratios. There are inquiries into the original poster's calculations and assumptions regarding the relationship between weight and gravitational acceleration.

Discussion Status

Several participants have pointed out a potential error in the original poster's calculations, specifically regarding the squaring of the radius in the formula. There is a collaborative effort to identify and correct this mistake, indicating a productive direction in the discussion.

Contextual Notes

Participants emphasize the importance of correctly applying the gravitational formula and the non-linear relationship between weight and gravitational acceleration. There is an acknowledgment of common mistakes related to squaring terms in calculations.

brad sue
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Hey!
I need help for this problem.

The mass of a hypothetical planet is 1/100 that the Earth and its radius is 1/4 that of the Earth. If a person weigths 150 lb on the earth, what would he weigth on his planet?

I tried the formula g=GM/r^2 by doing a ratio but I do not find the right answer.

Thank you
B
 
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well, g = GM/r^2 , all right ...
show me your actual work and I'll find your error.

(I suspect that you forgot to square the ¼ ...)
 
What exactly did you do? It's not going to be a linear relationship...
 
lightgrav said:
well, g = GM/r^2 , all right ...
show me your actual work and I'll find your error.
(I suspect that you forgot to square the ¼ ...)
gp= GMp/Rp2
gp= GMe/Re2
ge/gp=(Me/Mp)*(Rp/Re)=100/4=25
 
Yup, you forgot to square the denominator. It's R^2 remember?
 
yeah ... you know what that "2" is for ?

If you're likely to forget the square (most people are), write the r^2 as r . r .
 
Pengwuino said:
Yup, you forgot to square the denominator. It's R^2 remember?
OOPS! thank you
 

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