Question:

A certain neutron star has five times the mass of our Sun packed into a sphere about 10 km in radius. Estimate the surface gravity on this monster.

Source: Giancoli, Douglas C., Physics: Principles with Applications, 7th Edition, 2014.

Quick Answer:

$6.7 \times 10^{12} \textrm{ m/s}^2$

### Transcript for this Giancoli solution

This is Giancoli Answers with Mr. Dychko. The acceleration due to gravity on this neutron star is capital*G*—gravitational constant—times 5 times the mass of the Sun which is 5 times 1.99 times 10 to the 30 kilograms divided by the radius of the neutron star, which is 10 kilometers, or 10 times 10 to the 3 meters, squared. And then, that's about, 6.7 times 10 to the 12 meters per second squared or newtons per kilogram squared or newtons per kilogram, depending on which units you prefer. And that means that a dropped object would approach the speed of light in less than a second.