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Projectile Motion of a Man Problem

  1. Mar 2, 2014 #1
    1. The problem statement, all variables and given/known data

    A man stands on the roof of a building of height 14.1m and throws a rock with a velocity of magnitude 29.3m/s at an angle of 29.9 degrees above the horizontal. You can ignore air resistance.

    1) Calculate the maximum height above the roof reached by the rock.

    2) Calculate the magnitude of the velocity of the rock just before it strikes the ground.

    3) Calculate the horizontal distance from the base of the building to the point where the rock strikes the ground.

    2. Relevant equations



    3. The attempt at a solution

    1) 10.9 m, I know that's right

    2) 33.7 m/s, that's also correct

    3) 57.4 m, but this answer is wrong, I think

    this is how I worked it out
    x = Vx*t
    = 25.4*2.26 (The vertical time it took to drop from it's max height to the ground)
    = 57.4 m
     
  2. jcsd
  3. Mar 2, 2014 #2

    Doc Al

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    Staff: Mentor

    What about the time it took to rise to the maximum height?
     
  4. Mar 2, 2014 #3
    Ok so the time it took to rise to max height was 1.49's so the total flight time will be 2.26+1.49 = 3.75's

    So it should be,

    x = Vx*t
    = 25.4*3.75
    = 95.25 m, Correct ?
     
  5. Mar 2, 2014 #4

    Doc Al

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    Staff: Mentor

    Good.
     
  6. Mar 2, 2014 #5
    Thanks ! :)
     
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