More Physics Confusion

Discussion in 'General Off-Topic Chat' started by jonthedit, Oct 20, 2014.

  1. jonthedit
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    jonthedit GBAtemp Advanced Maniac

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    To find the initial velocity of this, what do I need to do?
    Ignoring Air resistance and Air Friction:
    [​IMG]

    [​IMG]

    I have found t, the total time it takes to reach the water, and the height maximum point, when the Vi = 0.
    I am lost how to find the initial velocity.

    I have tried

    deltaX
    / = v
    t

    ,

    trying: 16.05 / 2 (the current t) = 8.025m/s

    I have tried finding t for the triangle part I made only, being sqroot of (8.03/5).
    This makes the Vi = 12.6649m/s, which I think is too big of a number :|

    Finally, taking the total Xx distance, 13.9[total Xx]/2[original t]: I get Vi=6.95
     
  2. marcus134

    marcus134 GBAtemp Advanced Fan

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    where's your gravity? 9.81m/s²
     
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  3. jonthedit
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    jonthedit GBAtemp Advanced Maniac

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    That has to do with...?
    Also in this problem I get to assume gravity is 10m/s^2.

    I just care about my initial velocity. Gravity should not matter to find this... right?
     
  4. marcus134

    marcus134 GBAtemp Advanced Fan

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    he's diving, he obviously ain't gonna fly 8m high in the sky then hit a wall and fall straight into the water.
    it's a parabolic movement, the horizontal movement is constant, and the vertical is accelerated.
     
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  5. grossaffe

    grossaffe GBAtemp Addict

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    You said you already know how long it takes for him to hit the water, no? We'll call that t1. So then your initial velocity in the X direction = 13.9/t1. From there, you should be able to do trigonometry with the angle of the dive.
     
  6. jonthedit
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    jonthedit GBAtemp Advanced Maniac

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    I said that too, but with the math it does not matter.
    I am ignoring air resistance and friction. For purposes of equations, I can assume he hits a wall, because I do not care about his Xy descent, as I already know the change in Xy.
    The 30* angle and unknown speed provided will make it a superhuman jump and his speed is going to be ridiculous.
     
  7. marcus134

    marcus134 GBAtemp Advanced Fan

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  8. jonthedit
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    jonthedit GBAtemp Advanced Maniac

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    Correct answer Vi = 12.6649m/s
     
  9. Veho

    Veho The man who cried "Ni".

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    The correct solution is Vi=6,34 m/s

    Plug it back into the projectile motion formulae and all the numbers fit.


    [​IMG]
     
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  10. jonthedit
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    jonthedit GBAtemp Advanced Maniac

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    Still not following this... I don't get how I find V0, I get V0y and V0x
     
  11. grossaffe

    grossaffe GBAtemp Addict

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    V0 = sqrt((V0x)^2+(V0y)^2)
    V0 = V0y/(sin(30 degrees))
    V0 = V0x/(cos(30 degrees))

    Pick your poison.
     
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