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Homework Help: Intial speed of projectile motion from height

  1. Jun 13, 2010 #1
    ok im trying to find out how to work out the intial velocity of a projectile dropped from a height h and reaches a distance s.

    say a ball thrown from a height of 2.8 metres and reaches a distance of 3 metres.

    I want to be able to work it out WITHOUT having to work out the time.
    so cant use s=v*t

    does anyone kow What is the equation for this?
  2. jcsd
  3. Jun 13, 2010 #2


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  4. Jun 13, 2010 #3
    You must know these concept. All the vectors you must consider 2 components. Horizontal Motion velocity is constant and vertical motion acceleration is constant.If the particle dropped from the hill, no need to consider angle for initial velocity.
    Horizontal Motion Vertical motion
    initial velocity v(0x)= v(0) v(0y)=0 (for above case)

    final velocity v(x)=v(0x)=v(0) v(y)=.........

    acceleration a(x)=0 a(y)=-g

    displacement x y

    time t t (scalar)

    x=v(0x)t y=v(0y)t -0.5 gt^2
    v(y)=v(0y) -gt
    You may use simple free fall bodies equations.
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