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Homework Help: How far will this bullet drop in 3 seconds

  1. Jun 23, 2008 #1
    1. A bullet is fired horizontally from the roof of a building 100. meteres tall with a speed of 850 meters per second. Neglecting air resistance, how far will the bullet drop in 3.00 seconds?
    1) 29.4 m 2) 44.1 m 3) 100. m 4) 2,550
    Since the horizontal speed should be constant throughout, so I think 850 is the horizontal initial speed, so I did: 850*3=2550 m, but it's the wrong answer.

    2. A ball is being kicked by a foot and rising at an angle of 30 from the horizontal. The ball has an initial velocity of 5.0 meters per second. As the ball rises, the vertical component of its velocity 1) decreases 2) increases 3) remains the same
    I think it increases because the vertical component is 5*sin30=2.5, and once the angle increases, then it's 5*sin 45=3.54. So it obviously increased, but the answer is 1) decreases, so I don't know.

    Thanks a lot for help.
  2. jcsd
  3. Jun 23, 2008 #2
    hint for number one
    it's asking how far the bullet dropped, so find its y displacement, not x...

    hint for number two
    if the ball's velocity continued to increase it wouldn't come back down...also your velocity should look like V = Vosin@ - 1/2gt^2
    hope this helps
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