Throwing a dart from a roof - Velocity

  1. 1. The problem statement, all variables and given/known data

    A dart is thrown horizontally from a buildings rooftop. The dart's time of flight is 2.0 s. The dart sticks in the ground such that it makes a 53.1 degree angle with the ground.

    With what speed was the dart thrown?

    3. The attempt at a solution

    I am studying for my final and i do not get this problem from one of my previous tests.

    The answer is 14.7 m/s and i have no idea how to get it. Can anyone point me in the right direction.

    Thank you :)
  2. jcsd
  3. rock.freak667

    rock.freak667 6,231
    Homework Helper

    Well if it is throw horizontally, then the initial vertical velocity is zero right? Using an equation of motion, what would be final vertical velocity when t=2?
  4. Is the final vertical velocity when t=2 just 19.6 m/s

    I got that from

    Vf = Vi + at

    oh so then from that the x component of the Vf will be the same as the velocity initial correct?


    tan(53.1) = 19.6 / Vfx

    Vfx = 14.7 m/s

    Does that seem right?
  5. rock.freak667

    rock.freak667 6,231
    Homework Helper

    Yes that looks correct.
  6. Yay! thank you very much :)
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