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Homework Help: Projectile Motion

  1. Mar 12, 2009 #1
    1. A skateboarder starts at the bottom of a 1 metre ramp, with an incline of 30 degrees. The skateboarders initial velocity is 7m/s. How far will the skateboarder land from the end of the ramp?

    I firstly worked out the hypotenuse and adjacent lengths of the ramp. I then worked out the velocity of the skateboarder at the end of the ramp. I am having trouble with piecing together the projectile motion. Could somebody help me through this problem. Im not looking for an answer, just help.
  2. jcsd
  3. Mar 13, 2009 #2
    First thing is, is there any air resistance? Two other questions that will effect your answer, do you the force of gravity?

    If there is not, finding the displacement will be easier for you. The first thing is, you will need to know is the horizontal and vertical velocities.

    Do you also know what equations you will need?

    P.S. If there is no air resistance, remember that the vertical and horizontal velocities are separate from each other.
  4. Mar 15, 2009 #3
    Thanks for your response.If air resistance is not considered, how do I find out the vertical and horizontal velocities at the end of the ramp? For the equations, I would think just the usual kinematic equations, seperated into horizontal and vertical components.
  5. Mar 15, 2009 #4
    separating into horizontal and vertical components would be a good idea.

    If you consider just the vertical part of the problem, the period of the jump is going to just be how long it takes gravity to overcome the skater's upward velocity.
  6. Mar 15, 2009 #5
    it would be a very good idea to find out the vertical velocity, then with that, a lot of doors open up that leads to your answer.
  7. Mar 16, 2009 #6
    Im having trouble finding the y velocity. Im not sure where to start.
  8. Mar 17, 2009 #7
    Okay, Make a vector diagram of the ramp, the initial velocity at 30 degrees and you can then find the vertical velocity.

    Remember this: when trying to work out a problem that at first does not make sense, draw a vector diagram (if applicable), it is remarkable how useful they really are.
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