# Finding Peter Griffin's Mass

So I have this homework questions which asks me to watch this video on youtube:

I have determined that I can find the angular velocity of the object orbiting Peter by determining the period of the orbit.
w=2(pi)/T
Now I thought about equating the centripetal force and gravitational force together, then using the angular speed found, I could find the mass. However, there is a left over constant, the radius. I am not sure if there is anyway to eliminate it.

Any help would be appreciated!
Thanks
DoubleMint

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Pengwuino
Gold Member
Are you not allowed to estimate the orbital radii? I mean... if that's an absurd suggestion, then why ask an absurd question :P

The question is vague, no mention of estimating the orbital radii. I also came to the conclusion that there is no way to complete the question unless I have the value for the radius.
Thanks Pengwuino!

Pengwuino
Gold Member
Show us what you got for an answer, this might be pretty funny of a result.

Okay so i measured the period to be around 2.62s. Then the angular speed is 2(pi)/(2.62s) = 2.3981s^-1
F_c = F_g
m(w^2)r=Gm(m_p)/(r^2) where m_p is the Peter's Mass.
m_p=(w^2)(r^3)G^-1
r was estimated to be 0.15m
m_p = 2.9E8kg (roughly)
If I did it right, he is one heavy man :tongue: