For G i put 6.67 x 10^11 G = 6.67 x 10^11
For Me i put 6 x 10^24 kg Me = 6.0 x 10^24 kg
For T i put 28800 sec T = 28800 sec

What am I doing wrong? Are my steps correct? What are you getting for your answer?

Last edited:
D H
Staff Emeritus
One error: you didn't square the entire expression, $2\pi r/T$. However, correcting this will not fix the 1014 problem. As Dick noted, please show exactly what numbers you used.

nrqed
Homework Helper
Gold Member
For G i put 6.67 x 10^11 G = 6.67 x 10^11
For Me i put 6 x 10^24 kg Me = 6.0 x 10^24 kg
For T i put 28800 sec T = 28800 sec
G is 6.67 times 10 to the minus 11

D H
Staff Emeritus
G is 6.67 times 10 to the minus 11
Even more correctly, 6.67x10-11 m3/kg/s2. It is a good idea to always explicitly represent units.

nrqed
Homework Helper
Gold Member
Even more correctly, 6.67x10-11 m3/kg/s2. It is a good idea to always explicitly represent units.
You are right. I just wanted to emphasize the problem with the exponent.

D H
Staff Emeritus
You're right too. That is a very big problem.

Alright, I changed it and got 2.56 x 10^7 m for the radius of the orbit. . . Can someone work the problem out and see if this is the correct answer?

Also, no one told me if my final equation was correct... [2(pi)^2]r^3 = GmeT^2
Is this equation correct?

Last edited:
nrqed
Homework Helper
Gold Member
Alright, I changed it and got 2.56 x 10^7 m for the radius of the orbit. . . Can someone work the problem out and see if this is the correct answer?

Also, no one told me if my final equation was correct... [2(pi)^2]r^3 = GmeT^2
Is this equation correct?
I get $2.03 \times 10^7 m$ You forgot to square the 2. It's (2 pi)^2

OK. I did it and got 2.04 x10^7 m. I did you just round up in your calculation?

nrqed
Homework Helper
Gold Member
OK. I did it and got 2.04 x10^7 m. I did you just round up in your calculation?
I keep getting 2.03 x 10^7 m. I did not round off.
(I mean I rounded off my final answer but not in the intermediate steps)

OK. Weird, I did it again and got 2.03 x 10^7. Cool.

Thanks for your help and patience everyone, I guess I made this problem harder than it needed to be.

D H
Staff Emeritus