Question

I'm not sure if my answers are correct. Your help will be greatly appreciated. Thanks in advanced!

1. two very large cruise ships each have a mass of 415000 tonnes. If they were docked side by side, 1.0m apart, their centres would be 60m apart. What is the force of gravitational attraction putting them together? (hint: 1 tonne=1000kg)

2. On Earth, the gravitational field intensity is 9.8 N/kh. Mercury has a mass of 3.28x10^23kg abd a radius of 2.57x10^6m/ Calculate the gravitational field intensity on Mercury N/kg.

3. What would the weight of the dog be if it was taken to Mercury? (the weight of the dog is 245N and the mass is 25kg)

for #1 I got 3x10^-9, for #2 i got 8.5x10^15 and for #3 I got 2.1x10^17. I don't think I got these answers correct.

Answer 1

1.
F =G•m₁•m₂/R²
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg²,
F =G•m₁•m₂/R²=
=6.67•10⁻¹¹•(4.15•10⁸)²/60²=3191 N
2.
g`=GM/R²=
=6.67•10⁻¹¹•3.28•10²³/(2.57•10⁶)²=3.31 N/kg
3.
W(Mercury)=mg`=25•3.31=82.75 N