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Homework Help: Projectile trajectory (True/False)

  1. Sep 7, 2009 #1
    1. The problem statement, all variables and given/known data

    The figure represents the trajectory of a projectile going from A to F. Air resistance is negligible.


    2. Relevant equations

    For all the following sentences choose True or False:

    1. At point F the speed is the greatest?

    2. At point C the velocity vector has only an horizontal component?

    3. At points B and D the velocities are the same?

    4. At point C the acceleration is zero?

    5. The time it takes the particle to get from point A to point C is greater than the time it takes it to get from point C to point F?

    6. The horizontal component of the velocity at point E is the same as the horizontal component of the velocity at point A?

    7. Let →vD , →vE be the velocity vectors at points D and E respectively.
    The vector (→vE) − (→vD) is directed vertically downwards?

    3. The attempt at a solution

    I got as

    1. True
    2. False
    3. True
    4. False
    5. True
    6. False
    7. I didn't understand it.

    Now I don't know if these answers are correct or not.
    Last edited: Sep 7, 2009
  2. jcsd
  3. Sep 7, 2009 #2
    If we could see the diagram, that would be really helpful.
  4. Sep 7, 2009 #3
  5. Sep 7, 2009 #4
    For #5, why do you say it is true?
    As for #7, I'm not sure what the question is asking.
  6. Sep 7, 2009 #5
    Are the rest of the questions correct? except 5?
    7 is like, the arrows are on top of v, so it's like velocity vector
  7. Sep 7, 2009 #6
    I know, that's not what I don't get.
  8. Sep 7, 2009 #7
    So 5 is false, but then why is it false? Does it take the same time?
  9. Sep 7, 2009 #8
    Of course, it's symmetrical. Think of it as a parabola on a graph where time is on the x axis and meters are on the y axis. It takes the same time for it to get from A to C as it does for it to get from C to F.
  10. Sep 7, 2009 #9


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    Gold Member

    for 7# what do you know about horizontal component of particle’s velocity that follows Projectile trajectory?
  11. Sep 7, 2009 #10
    I wrote here all the information I had.
  12. Sep 7, 2009 #11
    There's also implied information. Since it's a projectile, you know that the x-components of the velocity vectors at all points are the same since there's no acceleration in the horizontal direction.
  13. Sep 7, 2009 #12


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    Gold Member

    I know, this is not about your Q but more [as a general role] you should know this, as Quincy said the horizontal component of the velocity is always constant, now knowing that the velocity at E> the velocity at D [you know why?] what do you think the answer is true/false?
  14. Sep 7, 2009 #13
    Here is what I got.
  15. Sep 9, 2009 #14
    That was awesome brother. I understood each and every question. Thanks for providing the reasons also. :)
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