# Pendulum and altitude

1. Feb 15, 2005

### 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.

2. Feb 15, 2005

### 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.

3. Feb 15, 2005

### sebasalekhine7

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

4. Feb 15, 2005

### 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.

5. Feb 15, 2005

### sebasalekhine7

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

6. Feb 16, 2005

### 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.

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