Find the force of gravity acting between at 1.7x10^30 kg planet with 5.5x10^20 kg moon that is 2x10^5 m away.
A) 4.0x10^30 N
B) 5.0x10^30 N
C) 4.3x10^30 N
D) 9.8x10^30 N

None of these answers are correct...

Applying the law of universal gravitation, we have

F = G m₁ m₂ / R²

where

G = 6.67 × 10⁻¹¹ N•m²/kg²

m₁ = 1.7 × 10³⁰ kg

m₂ = 5.5 × 10²⁰ kg

R = 2 × 10⁵ m

→   F = (6.67 × 1.7 × 5.5)/2² × 10⁻¹¹⁺³⁰⁺²⁰⁻¹⁰ N

→   F ≈ 15.59 × 10²⁹ N

→   F ≈ 1.6 × 10³⁰ N

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