Please bare with me, i'm not sure how to put in the maths on a forum like this.(adsbygoogle = window.adsbygoogle || []).push({});

Ok so i was asked to combine two equations to get a third, this I have done. The equation is M = v squared x r and then the producet of those divided by G.

M is the mass of a black hole

v squared is the velocity of an object orbitting the black hole

r is the radius of the object from the centre of the black hole

G is newtons universal constant of gravitation given as 6.7 x 10 to the minus 11.

3. The attempt at a solution

The maths I don't need help with, i'm sure I have that right, it's the units i'm struggling to understand.

v is given as Km s-1

r is given simply as Km

G is given as 1 m3 kg-1 s-2

This would give units of

(Km s-1)2 x Km

m3 kg-1 s-2

I'm sure Kg is the actual unit I should end up with but i don't see how i get there with thee units. Again I apologise for not being able to enter the maths a little better, hopefully i've explained it well enough.

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Working out the units, need help please

**Physics Forums | Science Articles, Homework Help, Discussion**