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I'm stuck with college physics

  1. Jan 30, 2008 #1
    [SOLVED] I'm stuck with college physics

    My college professor decided he didn't want to teach this chapter on Motion in 2D and 3D so he left us to teach ourselves. My first question is this
    A stone is catapulted at time t = 0, with an initial velocity of magnitude 19.6 m/s and at an angle of 37.2° above the horizontal. What are the magnitudes of the (a) horizontal and (b) vertical components of its displacement from the catapult site at t = 1.11 s? Repeat for the (c) horizontal and (d) vertical components at t = 1.77 s.
    I got A and C and to find B and D, i thought I would use the equation y=vsin(x)t - (-4.9 t^2). I got 19.191 for B and 36.33 for D but both are wrong. (this homework is online) Am I missing something? Thanks
     
  2. jcsd
  3. Jan 30, 2008 #2

    Hootenanny

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    Welcome to the forums,

    I haven't worked through your problem, but have you attempted rounding your answers to 3sf?

    Also, homework questions should be posted in the Homework forums.
     
  4. Jan 30, 2008 #3
    Well, I did try rounding, but SF doesn't matter for this online program, and sorry, I didn't know there was a homework section
     
  5. Jan 30, 2008 #4
    1. The problem statement, all variables and given/known data
    My college professor decided he didn't want to teach this chapter on Motion in 2D and 3D so he left us to teach ourselves. My first question is this
    A stone is catapulted at time t = 0, with an initial velocity of magnitude 19.6 m/s and at an angle of 37.2° above the horizontal. What are the magnitudes of the (a) horizontal and (b) vertical components of its displacement from the catapult site at t = 1.11 s? Repeat for the (c) horizontal and (d) vertical components at t = 1.77 s.


    3. The attempt at a solution
    I got A and C and to find B and D, i thought I would use the equation y=vsin(x)t - (-4.9 t^2). I got 19.191 for B and 36.33 for D but both are wrong. (this homework is online) Am I missing something? Thanks
     
  6. Jan 30, 2008 #5

    Hootenanny

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    The equation should be;

    [tex]y = u\sin\theta t + \frac{1}{2}at^2[/tex]

    Where u is your initial velocity and a=-g=-9.81 m/s/s.
     
    Last edited: Jan 30, 2008
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