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Homework Help: Projectile Motion trajectory Problem

  1. Sep 27, 2006 #1
    8. A Physics student on Planet Exidor throws a ball, and it follows the parabolic trajectory shown in Figure 6.8 (whille it will not be recreated on this forum, the figure shows a part of a parabolic curve which starts at the origin and peaks at t=2. It also shows the velocity vector at t=1, which will be entered later in the pst). The ball's position is shown at 1 s intervals until t=3s. At t=1 s, the ball's velocity is (2.0i + 2.0j)m/s, where i and j are unit vectors.

    a. determine the ball's velocity at t=0,2,and 3 s.
    b. what is the value of g on planet Exidor?
    c. what was the ball's launch angle.

    I know how to do parts b and c, but can't do either without a. I'm not sure what formula to use, but I do know the following:

    at t=1:
    v1=(2.0i + 2.0j)m/s

    ay=-g m/s^2


    Thank you in advance.
  2. jcsd
  3. Sep 27, 2006 #2

    Doc Al

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    Staff: Mentor

    Treat the vertical and horizontal components separately. Hints: What's the vertical component of velocity at the highest point? (t = 2) What about the horizontal component?
  4. Sep 27, 2006 #3
    Figured it out. since the velocity in the y direction is 0m/s at t=2s, I was able to calculate the gravity. I then used this to find the velocities at the other times. I don't know if using part b to solve part a is correct, but I can check my instructor's webpage to see if it gets the correct answer.
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