- #1

1st2fall

- 22

- 0

## Homework Statement

Certain neutron stars (extremely dense stars) are believed to be rotating at about 6 rev/s. If such a star has a radius of 15 km, what must be its minimum mass so that material on its surface remains in place during the rapid rotation?

G=6.67*10

^{-11}m

^{3}kg

^{-1}s

^{-2}

## Homework Equations

[tex]F_c{}=\frac{mv^{2}}{r}[/tex]

[tex]F_g{}=\frac{GM_1{M_2{}}}{r^{2}}[/tex]

## The Attempt at a Solution

30[tex]\pi[/tex]km*6rev/s=180[tex]\pi[/tex]km/s

which gives the linear velocity of something on the surface of the neutron star... but I'm clueless as to how to arrive at a mass of the star from it. I could the Centripetal acceleration but I'm not sure how that's related here. the only thing I can think of there is setting the centripetal acceleration equal to the gravitation acceleration which gives

Gm/r

^{2}=v

^{2}/r

m=v

^{2}r/G

which yields something like 7.28635682 × 10^24(kg?)

I'm just looking for advice on what I'm actually looking to do. I don't know what I should be looking for...