Gravitational Attraction Question

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SUMMARY

The discussion focuses on calculating the point between the Earth and the Moon where gravitational forces cancel each other out. The mass of the Moon is established as 7.35x10^22 kg, and the distance between the Earth and the Moon is 3.84x10^5 km. Participants utilize the gravitational force formula, Fg = Gm1m2/r², to derive expressions for gravitational attraction from both celestial bodies, ultimately leading to the equation GMe/X² = GMm/(D-X)² for solving the position X. The conversation emphasizes the importance of maintaining symbolic representations until a final numerical solution is reached.

PREREQUISITES
  • Understanding of gravitational force calculations using Fg = Gm1m2/r²
  • Familiarity with algebraic manipulation and solving equations
  • Knowledge of mass values for Earth (5.98x10^24 kg) and Moon (7.35x10^22 kg)
  • Basic understanding of distance measurement in meters (1 km = 1000 m)
NEXT STEPS
  • Learn how to derive gravitational force equations for multiple bodies
  • Study the concept of gravitational equilibrium points in celestial mechanics
  • Explore numerical methods for solving nonlinear equations
  • Investigate the implications of gravitational forces in orbital mechanics
USEFUL FOR

Students in physics, educators teaching gravitational concepts, and anyone interested in celestial mechanics and gravitational interactions.

  • #31
the { } is square root
 
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  • #32
wilson_chem90 said:
the { } is square root
Ah, okay. Then yes, this is correct:
wilson_chem90 said:
alright so the new equation should be X/{Me} = D-X/{Mm}
Next is to solve that equation for X.
 
  • #33
i got to X = D-X{Me} / {Mm}
 
  • #34
wilson_chem90 said:
i got to X = D-X{Me} / {Mm}
OK, write that as:
X = (D-X) {Me/Mm} (using {} for square root)

Now solve for X. (Get all the X terms on the same side.)
 
  • #35
so would it just be X+X = D {Me/Mm}
 
  • #36
wilson_chem90 said:
so would it just be X+X = D {Me/Mm}
No. Realize that:

X = (D-X) {Me/Mm} →

X = D{Me/Mm} - X{Me/Mm}
 
  • #37
oh okay, yeah i remember that now, is that the final equation though?
 
  • #38
What do you mean by "final"? You still have to solve for X.
 
  • #39
well i have to isolate the other x right, but the only think i can think of is it would be X^2 = D{Me/Mm} - {Me/Mm}
 
  • #40
wilson_chem90 said:
well i have to isolate the other x right, but the only think i can think of is it would be X^2 = D{Me/Mm} - {Me/Mm}
No. You must isolate X, but you don't end up with X^2.

How would you solve this one?

x = a -bx (a and b are just constants)

It's the same basic equation.
 
  • #41
would it be x = a/b?
 
  • #42
wilson_chem90 said:
would it be x = a/b?
No. Do it step by step:

x = a - bx

group the x terms on the left:
x + bx = a

factor out the x:
x (1 + b) = a

isolate the x by dividing both sides by (1 + b):
x = a/(1 + b)

done!
 
  • #43
YES! finally, thank you so much. i appreciate your time and patience with me
 

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