Measuring gravitational field on another plane with a pendulum

Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
5 replies · 4K views
chara76
Messages
10
Reaction score
0

Homework Statement



An astronaut arrives at a new planet, and gets out his simple device to determine the gravitational acceleration there. Prior to this arrival, he noted that the radius of the planet was 7040 km. If his 0.400-m-long pendulum has a period of 1.0 s, what is the mass of the planet?

Homework Equations



T = 2pi * sqrt(L/g)

The Attempt at a Solution



g = (4pi^2*(0.400))/1^2 = 15.79 m/2^2

I was given this equation as a hint, but I can't figure out where to go from here to get mass.
 
Physics news on Phys.org


Ok, this is what I get:

g = (GM)/r^2 --> 15.59=[(6.674x10^-11)(M)]/7040000

M=1.6656 x 10^18 kg

Is this correct?
 


Thanks for catching that. How does this look?

g = (GM)/r^2 --> 15.59=[(6.674x10^-11)(M)] / (7040000)^2

M=1.17275 x 10^25 kg