🚀 go-pugleaf

Jack Jiang wrote:

> You guys are confused by the �reference FRAME s� problems.
> 
> A similar question is: If a meteoroid having mass m and velocity v, hits on
> Earth having mass M. What is the amount of kinetic energy caused by this
> collision?
> 
> According to meteoroid�s frame, the answer is 1/2 Mv ^ 2. But, this is a crazy
> amount and obvious false!
> The true answer should be about 1/2 mv ^ 2, based on Earth FRAME centered at
> Earth�s center. Every body agrees?

Nope.

First of all kinetic energy is not caused by the collision.  Kinetic
energy
already exists prior to the collision and is changed into something
else.

Furthermore the *total* kinetic energy in the collision is 

             .5mv(1)^2 + .5Mv(2)^2

M is mass of the Earth, 
v(1) is the velocity of the meteorite
V(2) is the velocity of the Earth

Obviously v(1) and v(2) are measured in the same reference plane in
order to account for a head on collision as opposed to a "catch up"
collision.

There is no "frame of reference" in a situation like this.  The energy
in
the system is cumulative, although of course the effect on the Earth is
negligable.

--
Keith Morrison
lonewolf@nbnet.nb.ca