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Physics
Energy
Kinematics

What would the kinetic energy of a rock sitting on the ground be?

Answer

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April 21, 2009 10:47PM

Zero.

You need to think in terms of "frame of reference" as in what are you comparing the rock to. If you are an observer sitting next to the rock then the kinetic energy of the rock RELATIVE TO YOU is zero - I.E. the rock isn't moving relative to you and thus has no kinetic energy - energy of motion - relative to you.

If you are an observer sitting a million miles from earth watching the rock then it is zipping around at 1000 miles per hour as the earth spins on its axis and it has significant kinetic energy RELATIVE TO YOU. You need to think in terms of "frame of reference" as in what are you comparing the rock to. If you are an observer sitting next to the rock then the kinetic energy of the rock RELATIVE TO YOU is zero - i.e. the rock isn't moving relative to you and thus has no kinetic energy - energy of motion - relative to you.

If you are an observer sitting a million miles from earth watching the rock then it is zipping around at 1000 miles per hour as the earth spins on its axis and it has significant kinetic energy RELATIVE TO YOU. ---- So we don't get bored, no kinetic and no gravitational potential energy.