> Seems like needing the piston to change directions is a waste of momentum.
It's not, in a closed system momentum is conserved [1] so without friction, a free engine would rotate forever.
Also there is not conceptual difference between an engine and a ball sniping in a donut. In both case, the piston or the ball have to change direction (the piston has to change direction more abruptly though)
It's not, in a closed system momentum is conserved [1] so without friction, a free engine would rotate forever.
Also there is not conceptual difference between an engine and a ball sniping in a donut. In both case, the piston or the ball have to change direction (the piston has to change direction more abruptly though)
[1] http://en.wikipedia.org/wiki/Momentum#Conservation