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    I don't get why the initial velocity is 0 when you fire a rifle. This is from one of the past paper questions. I know the initial velocity = 0 when you drop something, and when you throw something up initial velocity ≠ 0. But I don't understand the case when you fire something horizontally.
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    The initial velocity is not zero - the initial VERTICAL velocity is zero if you fire horizontally.

    Put it another way, a horizontal velocity has zero vertical component.
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    (Original post by phys981)
    The initial velocity is not zero - the initial VERTICAL velocity is zero if you fire horizontally.

    Put it another way, a horizontal velocity has zero vertical component.
    Right, I sort of get it now. But how about final vertical velocity?
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    You have to calculate that using equations of motion.

    You do it exactly as though the object had been dropped - in other words the fact that it is moving horizontally has NO effect on the vertical velocity.
 
 
 

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