# Calculating net gravitational force on the

**1. The problem statement, all variables and given/known data**

The drawing (not to scale) shows one alignment of the sun, earth, and moon. The gravitational force vector F SM that the sun exerts on the moon is perpendicular to the force vector F EM that the earth exerts on the moon. The masses are: mass of sun = 1.99 1030 kg, mass of earth = 5.98 1024 kg, mass of moon = 7.35 1022 kg. The distances shown in the drawing are rSM = 1.5 1011 m and rEM = 3.85 108 m. Determine the magnitude of the net gravitational force on the moon.

**2. Relevant equations**

F=G m1m2/r^2

Fnet = √(F1^2 + F2^2)

G = 6.674×10^-11

**3. The attempt at a solution**

For the force between the Sun and the Moon I got 4.04×10^20 and for the force between the Earth and the Moon i got 1.97×10^20 N and then for the net force I got 4.49×10^20 N

I really don’t know where I went wrong. I’m guessing my exponents are probably messed up? I’ve double and triple and quadruple checked it and I feel like my answer is right but WebAssign is saying I’m wrong. The calculations I used were

F(Sun and moon) = (6.674×10^-11(1.99×10^30 x 7.35×10^22)/(1.55×10^11)^2

Like I said, I got 4.04×10^20 N

F(Earth and moon) = (6.674×10^-11(5.94×10^24 x 7.35×10^22)/(3.85×10^8)^2

1.97×10^20 N

Fnet = √((4.04×10^20)^2 + (1.97×10^20)^2)

4.49×10^20 N

Thanks for any help!

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