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Positions Versus time on an incline

  1. Oct 4, 2015 #1
    The initial position of the block is the origin; i.e., x = 0 at t = 0 . Consider down the track to be the positive x-direction. A block with an initial velocity v0 slides up and back down a frictionless incline. Which graph best represents a description the position of the block versus time?

    There's several graphs, some sinusoidal, some completely flat, some like absolute value, etc. There are also qa semicircle shaped one, which is what I picked. #10 on this (pdf) has an image of each graph.

    It would make sense to me that this graph would look like a projectile motion graph, since the velocity decreases due to gravity as the object slides up the ramp, eventually comes to a stop, and slide/falls back down, accelerating due to gravity. Apparently this isn't correct. Is this somehow different from projectile motion?
     
  2. jcsd
  3. Oct 4, 2015 #2

    BvU

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    Hello ME22, welcome to PF :smile: !

    Please do use the template. We are not allowed to help you if you delete it.
    It's not clear what you are asking. You have an answer sheet pdf with no semicircular picture on it. The picture number 1. is marked as "correct" and has the features you describe. Why do you say "apparently this is not correct"?
     
  4. Oct 4, 2015 #3
    My bad. Here's a reposted version

    1. The problem statement, all variables and given/known data
    The initial position of the block is the origin; i.e., x = 0 at t = 0 . Consider down the track to be the positive x-direction. A block with an initial velocity v0 slides up and back down a frictionless incline. Which graph best represents a description the position of the block versus time?


    2. Relevant equations
    Concept Question

    3. The attempt at a solution
    It would make sense to me that this graph would look like a projectile motion graph, since the velocity decreases due to gravity as the object slides up the ramp, eventually comes to a stop, and slide/falls back down, accelerating due to gravity. Apparently this isn't correct. Is this somehow different from projectile motion?


    It's online HW. When I plug the right number in (multiple choice) I'm told I'm wrong. I lose points every time I answer incorrectly, so I'd completely lost as to what I'm missing.
     
  5. Oct 4, 2015 #4
    As it turns out, the question was inverted. I'll talk to my teacher about it the morning. I was worried I was totally missing the question!
     
  6. Oct 4, 2015 #5
    Is the initial velocity positive or negative?

    Remember that the slope of the position-time graph equals the velocity.
     
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