What is the gravitional acceleration near the surface of the star?

[missfearless017]

Neutron stars are extremely dense objects with a mass comparable to the mass of the sun but a radius of only several thousand meters. Consider a neutron star of mass M = 1.99e+030 kg and a radius of R = 10.8 km.

What is the gravitational acceleration near the surface of the star?

I tried using the equation gstar = G * mass / diameter^2 but that didn't work.

 

[neutrino]

You should be calculating the strength of the field (the acceleration) from the centre of the neutron star.

 

[missfearless017]

ok here's another one.

the gravitational acceleration on the surface of the moon is 1.622 m/s^2. An object weighs 9.8333 N on the moon (mass is 6.01427 kg). How many Earth radii must this same object be from the surface of the Earth if it is to weigh the same as it does on the surface of the moon?

I tried to calculate this one with g(moon) = G(mass of earth)/(nr)^2 but it didn't work.