Pendulum and altitude

[sebasalekhine7]

How can I measure altitude depending on the period of a pendulum? I know I have to calculate the value for g but I don't know how exactly altitude could be calculated.

[dextercioby]

Within "human limits",'g' is very weakly dependent upon altitude,but certainly,in principle,one can measure its values using a pendulum...

T=2\pi \sqrt{\frac{l}{g}}

g=\frac{GM_{E}}{(\bar{R}_{E}+h)^{2}}

Daniel.

[sebasalekhine7]

Sorry, but can you explain what the second formula means?

[dextercioby]

That is the acceleration of a body at height "h" about the surface of the Earth,due to Earths gravity...I'm sure it's not the first time u saw it...

Daniel.

[sebasalekhine7]

what is \bar{R}_{E} ?

[dextercioby]

The Average Radius of the Earth...??You know the one which you can compute,if you know the polar & equatorial radius and a bit of geometry.

Daniel.