I seems to be an paradox when working with energy. If a person going 20 m/s to 40 m/s the kinetical energy gain is (40^2-20^2)/2= 600 J.
Now imagine that i goinng in the opposite diraction with speed 10 m/s. Now the kinetical energy gain of the person is (50^2-30^2)/2=800 J.
I see this as an Paradox?
Maybe not, just an effect of two different moving reference frame...
