keplers 3rd law (1 Viewer)

[sf_diegoxrock]

hi could someone who knows how 2 use keplers 3rd law check my calculations??

mass = 4.858 x 10^24
period = 1.55 hrs

i got r=634 590.071

thanks !!

 

[tennille]

I got 6345.96 km. I'm not sure if you accidentally missed out on the "6" when you typed your answer up.

r^3/T^2 = GM/(4*pi^2)

G = 6.67*10^-11
M = 4.858*10^24
T = 1.55*60*60 = 5580 seconds

Just plug those values into the equation, and it gives you the radius in metres.

 

[Riviet]

I'll confirm Tennille's anwer:

Rearranging kepler's law we obtain:

r=[GMT²/4pi²]^1/3

= [(6.67x10^-11)(4.858x10²⁴)(5580²)/(4pi²
)]^1/3

=6345960.071m

Therefore Tennille was right in saying that you must have missed the 6 in the
answer.