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Homework Help: Vector problem (motion in a plane)

  1. Oct 27, 2013 #1
    1. The problem statement, all variables and given/known data
    A newspaper boy throws papers sideways onto the porches of his customers while riding his bicycle along the sidewalk. The sidewalk is 15m in front of the porches. The boy throws the papers at a horizontal speed of 6m/s relative to himself, and rides the bicycle at a speed of 4m/s relative to the sidewalk.
    Question: If he waits until he is directly opposite a porch, at what horizontal angle with respect to the sidewalk will he have to throw the paper to hit the porch?

    2. Relevant equations
    None really except for knowing how sine, cos and tan work.

    3. The attempt at a solution
    I did part a) and b) of this question. The full solution can be found here (Q. 159, solutions are at the end of the page): http://chatt.hdsb.ca/~irhs/irhs_web...nematics Extra Study Questions.pdf?Plugin=Box

    I don't understand how they made the last triangle (for part c.), specifically how they labeled one side "4m/s" and how they knew it was a right triangle.
    If you have a separate solution please share :)
  2. jcsd
  3. Oct 27, 2013 #2


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    Science Advisor
    Homework Helper

    Hi Ash! Welcome to PF! :smile:
    In the diagram, horizontal represents the line of the road, so the horizontal side of 4 represents the 4m/s of the bike relative to the ground.

    The vertical line represents the route that the newspaper actually takes (at an unknown speed) … it goes perpendicular to the road, since the newspaper is directly opposite the porch when it is thrown :wink:
  4. Oct 27, 2013 #3
    Thank you sooo much :biggrin: I finally see it!
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