Help with Universal Gravitation Questions

1. Find the Gravitational Force of attraction between a 2200 kg truck and 1100 kg car that are located fifteen meters apart? How large is this force compared to the force of a person pushing a button on a telephone (about 1 Newton of force)?

2. Calculate the Earth’s Gravitational Field Strength (in N/kg) on a 1 kg object located on the Earth’s surface 6380 km from the planet’s center.

F_g = gravitational force
G = universal gravitational constant (6.67 * 10^-11 N*m²/kg²)
m = mass
r = distance between centers

1.) Use the following equation, and solve for the gravitational force.
F_g = (Gm₁m₂)/(r)²
F_g = (6.67 * 10^-11 N*m²/kg²)(2200 kg)(1100 kg)/(15 m)²
F_g = 7.2 * 10^-7 N

2.)
F_g = (Gm₁m₂)/(r)²
F_g = (6.67 * 10^-11 N*m²/kg²)(1 kg)(5.98 * 10^24 kg)/(6.38 * 10⁶ m)²
F_g = 9.80 N

1) F = G M1 M2 / r^2

G = 6.67 x 10^-11
M1=2200
M2=1100
r=15

This should be very very less as compared to 1 N force should be of the order of 10^-7 or lesser.

2)gravitational strength at a distance r from a point mass is
g= GM/r^2 where M is the mass of point mass.

Since at earth surface the complete earth would be considered as a point mass, hence for M you substitute mass of earth. Look it up in table of constants in your book. r=6380x10^3 (must be in meters)

g should approximately come out to be 9.8m/s^2 (since F/m = acceleration)

Universal gravitation is defined by this equation:

F=G([M of a] • [M of b])/D^2

Lol it's sucks typing math. 

Force(F) equals the gravitational constant(G) multiplied my the masses of object A and B while all divided by the square of the distance(D) between them.

Btw, G = 6.67 x 10^-11 in (m^3)/(s^2 kg)