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Homework Help: Calculating vertical and horizontal components in projectile motion at a certain time

  1. Sep 9, 2011 #1
    1. The problem statement, all variables and given/known data

    A stone is catapulted at time t = 0, with an initial velocity of magnitude 20.5 m/s and at an angle of 41.4° above the horizontal. What are the magnitudes of the (a) horizontal and (b) vertical components of its displacement from the catapult site at t = 1.16 s? Repeat for the (c) horizontal and (d) vertical components at t = 1.70 s.

    I tried multiple solutions, but none of them are right, so I do not know what I am doing wrong.

    3. The attempt at a solution

    Ok so I think this is the closest I got to the answer, but I used the equation V=Vo(t)+(1/2)(a)(t)^2 So for the horizontal component at 1.16s I got x=20.5(1.16)+(1/2)(0)(1.16)^2 and I got x=23.78m. For the vertical component I got y=20.5(1.16)+(1/2)(-9.8)(1.16)^2 and y=17.18656m. For 1.7 seconds: x=20.5(1.7)+(1/2)(0)(1.7)^2 and I got x=34.85m for y: y=20.5(1.7)+(1/2)(-9.8)(1.7)^2 and y=20.689.
    (I think these were the closest answers I got, but I tried different methods which were all wrong so help is appreciated)
     
  2. jcsd
  3. Sep 9, 2011 #2

    NascentOxygen

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    Staff: Mentor

    Re: Calculating vertical and horizontal components in projectile motion at a certain

    The horizontal component of initial velocity is not 20.5

    The vertical component of initial velocity is not 20.5
     
  4. Sep 9, 2011 #3
    Re: Calculating vertical and horizontal components in projectile motion at a certain

    So, If I have the correct initial velocity, this method would be correct?
     
  5. Sep 9, 2011 #4

    NascentOxygen

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    Staff: Mentor

    Re: Calculating vertical and horizontal components in projectile motion at a certain

    Yes.
     
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