An apple weighs 1 Newton on the surface of the Earth. What would it weigh if Earth had twice the radius and four times the mass?

Question

I need help with this question.

Answer 1

R = radius of earth

M = mass of earth

m = mass of apple

W₁ = weight on surface = 1 N

W₁ = GMm/R²

W₂ = G(4M)m/(2R)² = (4/4)GMm/R² = GMm/R² = W₁

It weighs the same.