How you Determine the Order of Magnitude of the Mass of the Earth?

How you determine the order of magmitude of the mass of the earth?
- Dorcas (age 15)
Port Moresby,Papua New Guinea

Hi Dorcas,

You know that the gravitational force between the earth and and arbitrary object is F = M_e m G / R_e ² where G is the gravitational constant 6.6710^-11 Nm²/kg², R_e = 6.4*10⁶ m, and m is the mass of the object.   You also know that the force on the object is F = mg where g = 9.8 m/s²  is the acceleration of an object due to the earth's gravity.   Solving for M_e you get  M_e = R_e ² g/G = 6*10²⁴ kgm.

LeeH

And you may wonder, where did the value for G come from? Cavendish got it by measuring the gravitational force betwen two known masses.  /mw

 

 

(published on 02/23/2015)