mfb said:
The kinetic energy of the rocket is 5000 J, but the kinetic energy of the projectiles is 5 GJ. You can't look at the kinetic energy of the rocket without ignoring the massive amount of energy that goes into the projectiles. The first projectile alone gets about 5 kJ. The last one gets about 4.9999999 kJ. A bit less - while the rocket gains a bit more kinetic energy there.
Thanks
@mfb, that I realize, but.. I can tamper the number so that the energy kinetic of one the projectile could be negative.
I mean, from a rest observer where the rocket starts, if the rocket is fast enough, and wrt to a rest observer, one of the projectile could have the same direction as the rocket. Because in rocket's frame, the velocity of the projectile is minus, but wrt a rest observer the velocity of the projectile could be positive.
I think, ignoring heat and miniscule interstellar medium friction the energy kinetic of both the rokect and the projectile should be zero. I mean there were two walls, one wall hit by the rocket (and some projectiles if they are in the same direction as the rocket) and the other wall hit by the projectiles (the ones with the reverse direction as the rocket) so I think the energy kinetic will be the some for both wall? Except for a projectile with zero velocity.
I'm sorry, I just can't arrange my question.
Actually I'd like to study two scenarios.
A rest observer sees a rocket travels 100 km/s at the east.
And that rocket fires a half of its mass backward say 10 km/s, so the velocity of the object is 90 km/s while the velocity of the rocket is 110 km/s
From a rest observer wrt rocket, it will see the rocket (now) travels 10 km/s to the east and the projectile 10 km/s to the west.
And I still don't understand the relation of Newton and watt.
Say, a stationary rocket fires a projectile backward, after the effect of the acceleration diminish (now the rocket travels constantly), say 1 second after that the rocket fires another projectile.
After the effect of the acceleration diminish (now the rocket travels constantly), say 1 second after that the rocket fires another projectile.
After the effect of the acceleration diminish (now the rocket travels constantly), say 1 second after that the rocket fires another projectile.
and on and on,... why Watt increases over time?
I know, Newton doesn't work that way, to calculate Energy we use J = N * m. In above scenario, the acceleration only felt for each second.
Say, to fire a projectile backward in V velocity, the rocket needs W watt (is this a correct statement)?
Now, after 1 second, the effect of the acceleration diminish, the rocket fire another projectile with V velocity that neewds W watt, of course along the journey the power doesn't increase, right?
Or I could have edit my previous statement.
Now, after 1 milisecond, the effect of the acceleration diminishes, the rocket fire another projectile with V velocity that neewds W watt, of course ...
Now, after 1 microsecond, ..., the rocket fire another projectile with V velocity that neewds W watt...
I could have wrote 1 pico second, and from up here it looks like dt, constant acceleration. Just how hard it is to push a projectile backward in T0 and in T100 seconds?
I've
studied read special relativity in PF Forum for 1 year, and I realize that there's no absolute frame of reference in this universe, so what's so special about time zero, when the rocket starts travel and time 100 after 100 seconds that the rocket needs more power to push another km/s as at the first place?
Thanks, I do appreciate your answer.
By "special relativity" I mean constant speed in 1 spatial dimension.