Physics (Online w/ no teacher)
posted by Katie .
The mass of a certain neutron star is 3.0 X 10 to the 30th (1.5 solar masses) and its radius is 8,000 m (8 km). What is the acceleration of gravity at the surface of this condensed, burnedout star?
My answer was 31,265,625 X 10 to the 12th km/s squared.

F/m= GM/r^2= 6.67E11 * 3.0E30/64E6 m/s^2
= yes, you are correct, except your number of significant digits is far excessive. 
The answer is G M/R^2, where G is the universal constant of gravity,
6.67*10^11 N m^2/kg^2.
You missed the decimal point by a very wide margin, and you have too many significant figures.
The correct answer is 3.1*10^12 m/s^2 
Thank you both!