How to find the force exerted on a particle on the Earth by the Sun

[Vitani11]

Homework Statement

Find the force exerted on a particle on the Earth by the sun.

Homework Equations

F = - GMm/r²

r = distance between sun and particle
M = mass of sun
G = Gravitational constant
m = ?

The Attempt at a Solution

Should I be using the other mass as that of the earth, or that of a pebble? I think it is the pebble. I mean it's the force BY the sun ON the pebble, but I want to make sure.

 

[Hiranya Pasan]

Yes, in this case you should use the mass of the pebble