On Wed, Jul 21, 2010 at 11:36, <> wrote:
> Does anyone on this list know how speed/acceleration work in relation to
> required energy/mass?
Yes i am reasonable conversant in basic physics.
> Theres something Im not understanding. Heres a
> sample situation:
>
> A 100 tonne starship comes into existence in deep space (how it got there
> is irrelevant). It has unlimited fuel and can accelerate at whatever Gs
> its captain wants without harm to the captain (who is the only person on
> board). The captain accelerates the ship at 1 G in a particular direction
> (which direction is not important).
>
> Now, the energy needed for the ship to remain motionless is nothing at
> all, right?
>
> The energy needed for the ship to accelerate, measured in tones of thrust,
> is 10 tonnes of thrust per 1 G of acceleration per tonne of ship = 1,000
> tonnes of thrust, right?
>
Ok, your kinda mixing units here. A ton of thrust is a ton of thrust, so it
generates a impulse of 1 ton at one g. i.e. a 100 ton ship requires 100 tons
of thrust to accelerate at 1 g. Which addresses the force question.
>
> Okay, lets say the ship accelerates up to a certain speed; say 1,000 km
> per hour (it doesnt really matter). How much energy is required to
> remain at that speed? I would assume none as the ship would simply be
> drifting.
You are correct zero
> Now, if the captain wanted to start accelerating again at 1 G, how much
> thrust will he need? It will be 1,000 tonnes of thrust again, right?
Yes it will be the 100 tons of thrust again.
>
> Now for something slightly different. Einstein said that the force of
> gravity was the same force as that which you notice when you accelerate.
> So, if thats true, the ship will never actually *not* be near a source of
> gravity as long as it is accelerating, because if it is accelerating it
> *is* a source of gravity. This gravity, however, would only be present
> when accelerating, and not when drifting, would it not?
>
Simulated Gravity at thrust.
>
>
> So the ship is getting speedier and measurements are starting to change.
> Apparently this is because energy equals mass (with the numbers depending
> on how you measure it). The faster you go, the more mass you have. No no
> no, that cant be right. Going a certain speed does not require any
> energy at all. Only accelerating up to that speed requires energy.
> Right?
>
It depends on your frame of reference. its all relative.
> This should mean that if the ship accelerated to near-light speeds, and
> then stopped accelerating and coasted at that speed for a while, while it
> is just coasting time is behaving normally (due to there not being any
> gravity well when coasting) and the ships mass is 100 tonnes because its
> not using any energy to accelerate.
>
> So, if this ship was coasting at such a speed that, if it started to
> accelerate its mass would double, is this change in mass instant?
>
There is no change in mass from the ship's point of view. Nothing has
changed.
> I think one of my assumptions may be wrong, but I dont know what one.
> Can anyone help?
>
I would take a run at relativity if I where you.
--
Evyn