physics
posted by krista .
calculate the centripetal acceleration of the earth in its orbit around the sun and the net force exerted on the earth. What exerts this force on the earth? Assume that the earth's orbit is a circle of radius 1.50x10^11m. (earth's mass= 5.98x10^29kg, Sun's mass= 1.99x10^30kg)

Get the velocity of the earth in its orbit from
V = (2 pi R)/P
P is the orbital period, which is one year converted to seconds. R is the Earth's orbital radius.
The centripetal acceleration of the Earth is a = V^2/R.
The force exerted on the Earth by the sun is Me * a
where Me is the mass of the Earth. 
A satellite used in a cellular telephone network has a mass of 2010kg and is in a circular orbit at a height of 770km above the surface of the earthWhat is the gravitational force Fgrav on the satellite?
Take the gravitational constant to be G = 6.67×10−11N⋅m2/kg2 , the mass of the earth to be me = 5.97×1024kg , and the radius of the Earth to be re = 6.38×106m .
What fraction is this of the satellite's weight at the surface of the earth?
Take the freefall acceleration at the surface of the earth to be g = 9.80m/s2 .