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Quuuick Help Please!

  1. Jul 11, 2008 #1
    1. The problem statement, all variables and given/known data
    Consider one complete orbit around Earth as taken by astronauts aboard a space shuttle. The magnitude of the average velocity is equivalent to the average speed.



    2. Relevant equations



    3. The attempt at a solution
    Now this question asks me if its true or false now i drew it and the velocity cant be equivalent to the average speed so im confused could some1 tell me what they think it is

    i think its FALSE
     
  2. jcsd
  3. Jul 11, 2008 #2

    kreil

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    velocity is a vector, meaning it has magnitude AND direction

    speed is a scalar, meaning it only has magnitude

    For example, if I told you I was going 55 mph due North, I would have given you a vector. If I simply told you I was going 55mph, this would be a scalar since you don't know the direction.

    However, speed is defined to be the magnitude of the velocity. Why? Well, the magnitude of the velocity doesn't specify a direction, so it too is a scalar. Using the above example, the magnitude of the velocity is 55mph, and my speed is 55mph, therefore the magnitude of the velocity equals the speed.

    Therefore, I think this is TRUE
     
  4. Jul 11, 2008 #3
    OOOOOOO thank you see i get confused with that now this one is tricky to:

    The velocity of a passenger with respect to a train moving east would be less if the passenger is walking west at a particular speed than it would be if the passenger is walking east at the same speed.

    I got this to be true but it confused me with the wording what do you think?
     
  5. Jul 11, 2008 #4

    Dick

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    Can't really agree with you there. What is the average velocity? It's a vector, right? What's the magnitude of that average velocity?
     
  6. Jul 11, 2008 #5
    so am i right its false?
     
  7. Jul 11, 2008 #6

    Dick

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    Yes, it's false. Tell me what the average velocity is.
     
  8. Jul 11, 2008 #7
    there was none it was just a true or false question how bout these 2:

    Consider a trip from your home to your school and back home again. The magnitude of your displacement is equivalent to your distance travelled.

    The velocity of a passenger with respect to a train moving east would be less if the passenger is walking west at a particular speed than it would be if the passenger is walking east at the same speed.

    i think they are both true
     
  9. Jul 11, 2008 #8

    Dick

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    If you can't tell me what the average velocity of the shuttle is over one orbit, then you don't really understand why the first one is false. Ditto for the next one, what is the displacement? For the last one, the velocity is that of the passenger RELATIVE to the TRAIN. I think it's FALSE.
     
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