Question

Neptune has a mass that is about 17 times the mass of Earth. The distance between the Sun and Neptune is about 30.1 times the distance between the Sun and Earth.

If the gravitational force between the Sun and Earth is 3.5 x 1028 N, which is closest to the force between Neptune and the Sun?

6 x N
6 x N
6 x N
6 x N

Answer 1

Use inverse-square law scaling:

F_N = F_Earth * (M_N / M_E) / (r_N / r_E)^2
= 3.5×10^28 N * 17 / (30.1^2)

30.1^2 ≈ 906, so factor ≈ 17/906 ≈ 0.01877.
Thus F_N ≈ 3.5×10^28 × 0.01877 ≈ 6.6×10^26 N.

Closest choice: 6 × 10^26 N.