dcbwhaley wrote:
But if a rocket from Ursa Major were to smash into the side of the car it would move rapidly in the direction of Polaris with no corresponding movement in the opposite direction
How utterly stooopid!
There is acceleration of some component of the system towards Ursa Major (away from what I assume is Polaris for your example); the problem here is that you don't understand what it is.
The car accelerates towards Polaris; the rocket accelerates towards Ursa Major. So no problems there!
For your latest example: ? [of rocket] + ? [of car and planet it is on] before the collision is still the same as ? [of rocket + car + planet]. So how can you prove this wrong?
Let's reduce your example to prove the silliness of your claim.
Initial conditions: a snooker ball (2) from Ursa Major travelling at 1010m/s, heads straight towards another identical snooker ball (1) again from Ursa Major travelling at 1000m/s
(as seen relative to an observer moving at 1005m/s in the direction of Ursa Major)Event: the two collide and (for argument's sake) meld with each other.
Rest state: the combined speed will be 1005m/s.
?(1) + ?(2) = ?(1+2). Momentum is conserved!
(1) accelerated by 5m/s away from Ursa Major; (2) accelerated by 5m/s towards Ursa Major - there's your "corresponding movement in the opposite direction". Momentum of the system is still conserved!
What is your problem with that, Dave!!
If you want to expand it wider to consider variables you will invariably will claim that disprove the conservation of momentum: the net momentum of: whatever the rocket took off from, the rocket gases, the rocket, the car (and it's subsequent fragments) (and the planet it is on),
is conserved,
from initial conditions to rest state.
System closed; job done!
If you can't see how momentum is conserved, then your model is somehow wrong (be it incomplete).
How can someone of your claimed calibre not understand this simple and fundamental concept?
dcbwhaley wrote:
Are you claiming that momentum is conserved in ac losed system even when an external force is applied?
Misrepresentation! Ever the clue of a failed argument, or trolling…
Steve previously wrote:
if an external force is applied to a system, then the system isn’t isolated; otherwise the momentum is conserved.
Moreover, I made the same parallel with energy:
Steve previously wrote:
If external energy is applied to a system, then the system isn’t isolated; otherwise the energy is conserved.
...which, rather strangely, you didn't dispute; yet you still consider the two attributes to be different in this respect.
So Dave, tell us your claimed
difference between the "conservation of momentum" and the "conservation of energy";
how does one fail where the other succeeds?By your logic, you seem to be claiming that external
energy can be introduced into an otherwise closed system and that
energy is still conserved; can you clarify this. If that’s not the case, then please do explain the difference between that and what you are saying with externally affected
momentum.
I would love to see you try to reconcile that one!
Last, but certainly not least:
dcbwhaley wrote:
Of course. In those circumstances with no external force (i.e force from outside the closed system) applied momentum will be conserved.
You just accepted my original point !?!You've just accepted there need not be an external force for the accelerating car example - you've just agreed that momentum is actually conserved for
your same example explaining otherwise You've just inherently shot yourself in the foot
System closed; argument closed!
Can we move on?