O27PMR, my understanding is (ready to be corrected
) ... It'd move toward the back because it has mass and as Newton's 1st law of motion states - a mass will remain at rest or continue at its existing velocity unless an external force is applied. The acceleration of the plane is being applied to the helo only via the air around it, which'll be much less force than the inertia of the mass of the helo. The force you feel in your back as the a/c accelerates when you're in it is the accelerating force being applied to your mass (as it were
).
What I really don't get though, is the speed of light piece ...
. Isn't an object's mass meant to change as it approaches the speed of light? if so, then what's the story with 2 objects travelling away from each other at half the speed of light each? Their mass won't change (?) yet relative to each other they're doing the speed of light. Confuses the heck out of me
