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Homework Help: Problem with Projectiles

  1. Dec 2, 2008 #1
    1. The problem statement, all variables and given/known data
    On a snowy winter day, you decide to slide off the roof of your home. The roof has an angle of inclination equal to 25.0 degrees. Given that you leave the edge of the roof with a velocity of 5.36m/s and the edge of the roof is 9.25m above the ground level. Determine:

    a)Your total horizontal displacement
    b)Your total time of flight

    2. Relevant equations
    Vx = dx/t
    Vfy = Viy -gt
    Vfy(squared) = Viy(squared) - 2gdy

    3. The attempt at a solution
    First I wrote down what I was given and what I could easily derive:

    theta = 25(degrees)
    h = dy = 9.25m
    Viy = 5.36m/s
    g = 9.80m/s

    Vx = (cos(25))(5.36) = 4.8578 m/s

    Then I went:
    Vfy(squared) = Viy(squared) - 2gdy

    I then put in my values and the answer I got for Vfy is:

    Vfy = 14.5m/s

    Then I used the equation:

    Vfy = Viy -gt

    and I isolated the t and plugged in all my variables and the answer I got for t is:

    t = 0.933s

    Then I used the equation:

    Vx = dx/t
    (Vx)(t) = dx

    I then plugged in the two values (Vx and t) which I found out from my previous calculations and I got an answer for dx:

    dx = 4.53m

    b) For part "b" I used the equation:

    Vfy = Viy - 2gt

    then I isolated the t value and put in my values (some of which I found out in part a) to solve for t and I got:

    t= 0.933s

    I know this may seem like a really long question but could someone double check the answers that I got or tell me if the method I used in both question is correct or not? I would greatly appreciate it.
  2. jcsd
  3. Dec 2, 2008 #2


    User Avatar
    Homework Helper

    Re: Projectiles

    you leave the edge of the roof with a velocity of 5.36m/s in the direction of the inclination of the roof. There fore Viy = sin(25)(5.36)
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