Acceleration of Planet/Sun System

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Homework Help Overview

The discussion revolves around a problem involving gravitational acceleration in a planet-star system, specifically focusing on a planet with a mass five times that of Earth and located three astronomical units from a star with a mass one and a half times that of the Sun. The original poster is attempting to calculate the gravitational acceleration experienced by the planet and compare it to Earth's gravitational acceleration.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster calculates gravitational acceleration using the formula a=(GM1)/r^2 but questions whether they are interpreting the problem correctly, particularly regarding the wording of the question and the relevance of the planet's radius. Other participants express confusion about the phrasing of the question and suggest alternative interpretations.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem's wording. Some guidance has been offered regarding the interpretation of the first question, suggesting a focus on the acceleration due to the star's gravity at the planet's location rather than the planet's effect on the star.

Contextual Notes

Participants note that the original wording of the problem may lead to confusion, and there is an emphasis on ensuring that the calculations align with the intended question. The original poster is also considering the implications of comparing gravitational acceleration to that experienced on Earth's surface.

aurora7790

Consider a planet with a mass 5x that of the Earth a distance of 3AU away from a star with a mass 1.5x that of the sun.
-What is the acceleration of the planet due to gravity from the planet on the star?
-How does this answer compare with the acceleration we feel on the surface of the Earth g=9.8m/s^2? How many times larger or smaller is it?

*Remember that acceleration of a body with mass M2 toward a body with mass M1 is a=(GM1)/r^2

I assumed that I was looking for how the star's gravity affects the acceleration of the planets orbit but the second part, that asked how it differs from the Earth's acceleration, makes me wonder if I'm finding the force of gravity on the planet, but wouldn't that require the planets radius?

Anyway this is what I calculated using what I was given (Mp= mass of planet)
a=(GMp)/r^2=(6.67e-11)(5*5.977e24kg)/(3*1.5e11)^2= 9.84e-9 m/s^2
 
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Hello and wecome to PF!

aurora7790 said:
-What is the acceleration of the planet due to gravity from the planet on the star?
The wording of this question is very odd. Are you sure you typed it exactly word for word?
 
TSny said:
Hello and wecome to PF!

The wording of this question is very odd. Are you sure you typed it exactly word for word?
Yes I know the wording is what is throwing me off, it is typed exactly how it is on my worksheet
 
aurora7790 said:
Yes I know the wording is what is throwing me off, it is typed exactly how it is on my worksheet
That's too bad. The gravity "from the planet on the star" will not produce "acceleration of the planet".

The answer to the first question will relate nicely to the second question if you interpret the first question as:

"Calculate the acceleration of gravity produced by the star at the location of the planet."
or, equivalently
"What is the acceleration of the planet due to gravity from the planet on the star?
 
Last edited:

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