If you weigh 670 n on the earth, what would be your weight on the surface of a neutron star that has the same mass as our sun and a diameter of 25.0 km ? take the mass of the sun to be m s = 1.99×1030 kg , the gravitational constant to be g = 6.67×10−11 n⋅ m 2 /k g 2 , and the acceleration due to gravity at the earth's surface to be g = 9.810 m/ s 2 .

The weight of an object at the surface of a planet is given by:

where m is the mass and g is the gravitational acceleration, given by

where G is the gravitational constant, M is the planet's mass, and r the radius of the planet.

At Earth's surface, . Since we know the weight of the person at Earth's surface, F=670 N, we can find his mass:


Now we have to calculate the value of g at the surface of the neutron star. The mass of the neutron star is 25 times the Sun's mass:


While its radius is:


Therefore, the value of g at the neutron star surface is


Therefore, the weight of the person at the surface of the neutron star would be