Originally Posted by

**hvacrmedic**

Suppose you're stationed by the railroad track and you're watching a train pass by. You have good info that the mass of the train is X kg, and you measure its speed at Y m/s. You calculate it's KE as

kg(m/s)^2 or XY^2isn't this the formula for Force=ma, KE= 1/2mv^2

which in this case turns out to be a rather large number. A passenger on the train however measures the speed of the train as exactly 0 m/s. He calculates that the KE of the train is zero. It has no kinetic energy from his frame of reference. It should be obvious then that the KE that you attributed to the train is not an intrinsic property of the train, but rather just a perception, like color, relating to your particular frame of reference.