What is the proportionality constant for the Sun's gravitational force?

[moonman239]

This book that I'm reading mentions something where the gravitational pull of the Sun is proportional to that planet's mass/its orbital radius. What is this proportionality constant?

 

[mgb_phys]

Not quite , for an object in orbit the centrifugal force throwing it outwards is equal to the gravitational force pulling it into the object in the centre.

 

[moonman239]

Oh, okay. So really, F=(4pi^2mr)/T2 should be used.

 

[Janus]

This book that I'm reading mentions something where the gravitational pull of the Sun is proportional to that planet's mass/its orbital radius. What is this proportionality constant?

The gravitational pull on any planet by the Sun is proportional to that planet's mass divided by the square of its orbital radius. The actual formula is

$$F_g = G\frac{M_{sun}M_{planet}}{r_{orbit}^2}$$

where G is the gravitational constant and is equal to 6.673e-11 when M is measured in Kg and r in meters.