Posted by **Ashley** on Wednesday, January 30, 2013 at 6:19pm.

Calculate the kinetic energy that the earth has because of (a) its rotation about its own axis and (b) its motion around the sun. Assume that the earth is a uniform sphere and that its path around the sun is circular. For comparison, the total energy used in the United States in one year is about 1.1 x 1020 J.

- Physics -
**Elena**, Wednesday, January 30, 2013 at 6:30pm
(a) KE(rot) =I ω²/2

I=2MR²/5

ω=2π/243600 = ...(rad/ s)

Earths mass is M = 5.9710²⁴kg,

Earths radius is R = 6.37810⁶ m.

(b)

Linear velocity of the Earth is

v=ωr = 2π 1.49610¹¹ /365243600 =
m/s

KE=Mv²/2 =5.9710²⁴ (2π 1.49610¹¹ /365243600)²/2 =
J

- Physics -
**Ashley**, Wednesday, January 30, 2013 at 7:15pm
Thanks!! Clears up everything

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