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Another idea

  1. Sep 23, 2009 #1
    What if we don't NEED to use any force whatsoever to propel a vehicle? What if we could negate the net external force and just keep the vehicle going with a constant velocity with the appropriate magnitude? But what could we use to propel the vehicle at any given time and not add any other force as it is moving with a constant velocity(Also, this could stop speeding:D) - as we DO need to brake on the road:P Something not hazardous to the environment, so pollution isn't a problem.. we need something particulate and with a high enough magnitude - any suggestions?

    This is all seems too futuristic right now, but just an idea.
  2. jcsd
  3. Sep 23, 2009 #2
    I like your thinking outside of the box, but I don't really get your first sentence. How are you going to accelerate from a stopped position. No force = no acceleration.
  4. Sep 23, 2009 #3
    Sorry i must have worded it wrong. I mean, we need to use force to accelerate the vehicle - but then we could stop the external force, thus leaving a constant velocity. there's a lot of gaps, but i think we can work through it:)
  5. Sep 23, 2009 #4


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    Science Advisor

    Drive in a vacuum?
  6. Sep 23, 2009 #5
    I believe that it's impossible for a car to be 100% efficient, meaning that you will not be able to negate slowing forces on a car, which means you will always need some form of acceleration :(

    EDIT: Or take Nabeshin's idea haha
  7. Sep 23, 2009 #6
    Yes, nabeshin haha
  8. Sep 23, 2009 #7
    Yup, as long as we have to deal with gravity and atmosphere, we're going to need a Force to keep constant velocity.
  9. Sep 23, 2009 #8
    the question is - what is that force?
  10. Sep 23, 2009 #9


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    Staff: Mentor

    That's just another way of saying Newton's First Law of motion: objects require no external force to continue motion at constant speed.
  11. Sep 23, 2009 #10
    Have the vehicle travel in a tube in which there is a vacuum .. floating due to magnetic repulsion above current loop superconductors .. at the end of the trip, decelerate the vehicle with an electrical generator and Lenz's Law, so you get back some of the energy that was initially used to accelerate it.
  12. Sep 23, 2009 #11


    Staff: Mentor

    Once you reach orbital velocity you don't even need the magnetic repulsion for floating. At least, that was Heinlein's idea for a transit system on the moon.
  13. Sep 24, 2009 #12
    onto something
  14. Sep 24, 2009 #13


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    you need a force to accelerate a mass. and for a car like transport you need to cycle slowdown and go. because you are going allover the town. a futuristic system of cars travelling on rails merging and branching had allready been tested.(powered by elctricity)
    the problem with that is cost, just like those fancy magnetically lavitated trains which do have special uses but not general.
  15. Sep 24, 2009 #14
    In an imaginary world completely devoid of all resistive forces it is reasonable to assume that an object can continue moving with a constant velocity without an external force.We live in the real world where friction and air resistance are present.We can reduce these forces but not to zero.When an object moves with terminal velocity there are still forces acting on it but the resultant is zero.
    Last edited: Sep 24, 2009
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