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The transference of potential energy to kenetic energy and it's effect on momentum

  1. Oct 8, 2003 #1
    Lets say that you take an ultra modern spacecraft
    like Nasa is researching or may already have and
    equip it with a vast potential energy storage
    system.Before you embark on your flight a large
    quantity of potential energy is stored on board
    the ship.The craft is now accelerated to 50% of c
    in a straight line.Now we can agree that the craft
    possesses momentum x.The ship is travelling at 50%
    c and the vast quantity of potential energy,stored
    before the fight,is converted to very high speed
    particles stored in a ring on board the ship.
    Lets say the ships mass has increased by 20%,due
    to the conversion of potential energy to kenetic
    energy.The ship now possesses momentum y.If you
    decelerate the ship in straight line you now have
    an imbalanced force*time relationship between
    acceleration and deceleration.
    There are several possible explanations, the ship
    slows when potential energy is converted to
    kenetic energy,stored potential energy acts like
    mass,the ship does not act heavier when gaining
    kenetic energy, or something I've overlooked here.
  2. jcsd
  3. Oct 8, 2003 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Re: The transference of potential energy to kenetic energy and it's effect on momentu

    Wow, there really are a lot of misconceptions about special relativity packed into this paragraph. Let's see if we can begin to sort them out.
    You mean -- fuel?
    0.5c relative to the stationary earth, I imagine.
    Momentum depends on the observer. If "we" means specifically "observers on the earth," then sure, we'll call it x.
    Er, okay.
    Why should we say this? Where did this 20% figure come from? What sort of potential energy are we talking about?

    - Warren
  4. Oct 8, 2003 #3


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    Staff: Mentor

    My understanding was that energy is proportional to mass regardless of the form of the energy - stretch a rubber band (for example) and it gains mass.
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