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Homework Help: Predicting Time of Flight

  1. Nov 2, 2011 #1
    1. The problem statement, all variables and given/known data
    A system is setup to launch an object horizontally off desks with an initial speed of 4.2 m/s. Height of desk is 1.3 meters.

    What time of flight should be predicted for the object?


    2. Relevant equations
    Δt = (v2 - v1) / ∂ (Not too sure)


    3. The attempt at a solution
    1.3/4.2 = 0.31 seconds

    Hello. I tried to find the time, but I keep getting the time wrong. The actual answer is 0.52s, but I think I'm going the wrong way about it :( Can someone help me understand the question more and lead me into the right direction? I'm not very good at physics.
     
  2. jcsd
  3. Nov 2, 2011 #2
    Are you aware of the X and Y table method?

    Make an X and Y table
    Like this

    X___|___Y

    In the X column, put all of your X axis information (you have velocity)

    And in the Y column put down all of your Y axis information (you always have acceleration due to gravity, you have height/distance in this question as well)


    Now, remember that for horizontal you always use d = tv, and for vertical it's always d = vit + 1/2at^2.

    Use those formulae with the information you have in the respective columns to find the unknown variables.

    ALWAYS REMEMBER-
    Time will be equal in both columns, it is the only factor that does not change because it's neither an X nor a Y nor a Z vector, so if you get time in one column you will effectively have time in both columns.
     
    Last edited: Nov 2, 2011
  4. Nov 2, 2011 #3
    Ohh..! Thank you so much! You saved me!
     
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