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A packet is dropped from the window

  1. Nov 18, 2006 #1
    A helicopter is moving with some velocity in upward direction,a packet is dropped from the window of the helicopter.why the packet goes upward after dropping?What will be the velocity of the packet ?is its velocity is same as the helicopter?why,why?please explain.
     
  2. jcsd
  3. Nov 18, 2006 #2

    Doc Al

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    Initially, the packet moves with the same velocity as the helicopter. Why would you think otherwise?
     
  4. Nov 18, 2006 #3

    LURCH

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    When you drop an object from a stationary window, there is an instant during which your hand is no longer supporting it, but it has not yet started to fall. (In most real-world instances this moment is vanishingly brief but, in some cartoon situations it can last indeffinately, and largely deoends on how long it takes for the object to notice that it is unsupported.)

    If you repeat the same process in a vehicle that is moving upwards, the object still has a tendancy to remain "staionary" for an instant, but that means stationary relative to your hand, which means "moving upward" relative to the ground.
     
  5. Nov 18, 2006 #4

    Danger

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    Same idea as dropping something inside a train (similar to something in another thread). Although it drops straight down relative to the train, it describes a parabolic path relative to the ground.
     
  6. Nov 18, 2006 #5

    DaveC426913

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    Oddly, the OP seems to think that, initially, the packet actually goes up.
     
  7. Nov 18, 2006 #6

    Doc Al

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    Not so odd, since the helicopter is moving upward.
     
  8. Nov 18, 2006 #7
    Well,think of Newton's 1st law. The packet already has a velocity and will continue in that constant velocity. There will however, be external forces, air resistance and gravity which will pull it downwards. The reason the helicopter does not fall as well is that there is a force upwards exerted by the helicopter blades, well, making it able to fly in the first place.
     
  9. Nov 20, 2006 #8
    I am not understand please give me the reason that why the packet goes upward first.on the other hand the blades of helicopter are pushing air downward direction.then why the packet goes upward?
     
    Last edited: Nov 20, 2006
  10. Nov 20, 2006 #9
    True. But the air from the blades that pushes the packet down is a force. It CHANGES the velocity, not set the initial velocity. The initial velocity is set by the helicopter's velocity. In other words, it will keep on moving at that velocity since it is already moving upwards in the first place. Of course it will slow down and later fall but that is because of the existence of forces.
     
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