AL phsics (free falling)

An object falls from the top of a tower.

The object takes 0.4s to fall from the mid-point of the tower to the ground.

Calculate the time taken for the object to fall from the top of the tower to the ground.

Update:

reference ans. 1.37s

1 Answer

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  • 1 decade ago
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    Let the top of the tower to the ground be h,the speed of the object at the mid-point be v

    consider the motion from the middle to the ground

    h/2=0.4v+1/2x10x0.4^2

    h/2-0.8=0.4v

    v=1.25h-2

    consider the motion from the top to middle

    v^2-u^2=2as

    (1.25h-2)^2=2x10xh/2

    1.5625h^2-5h+1=10h

    1.5625h^2-15h+4=0

    h=9.3255

    h/2=ut+1/2at^2

    9.3255/2=1/2x10t^2

    t=0.9656

    time fall from the top to the groung=0.9656+0.4=1.37s

    Source(s): myself
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