projectile motion

Discussion in 'Physics' started by braddy, Sep 16, 2005.

  1. braddy

    Thread Starter Well-Known Member

    Dec 29, 2004
    83
    0
    Hi,

    Please somebody help me with this problem:

    A boy wants to knock down a coconut with a rock and his slingshot. He observes that the coconut is about 3.0m above his slingshot and the tree is 4.0m away along the ground.
    He knows from experience that the release speed of his rock is 20m/s.
    How far above the coconut should he aim?

    Please can someone help me?

    thank you

    B.
     
  2. haditya

    Senior Member

    Jan 19, 2004
    220
    0
    the equation of the projectile is given by
    y = x.v.tan p - 0.5*g.x.x.(sec p)^2

    put x=3,y=4 solve for p

    the height above which to aim is given by 3*tanp

    the 1st projectile equation is got by eliminating time t in the 2 equations given below
    x=v*cos p * t
    y=v*sin p * t -0.5g*t*t
     
  3. braddy

    Thread Starter Well-Known Member

    Dec 29, 2004
    83
    0
    Thankx I will try this
     
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