Acceleration of Planet/Sun System

[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

 

[TSny]

Hello and wecome to PF!

-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?

 

[aurora7790]

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

 

[TSny]

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?