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Homework Help: Projectile Problem - Time of Peak

  1. Nov 29, 2006 #1
    If a fireworks rocket has an initial upward speed of 58 m/s when launched, for how long will it coast before reaching its peak?

    So could I use the equation t=v0z/g?

    When I use this I get the peak to be 5.9s. Is v0z = 58 m/s or would that be 0? Am I approaching this correctly?
  2. jcsd
  3. Nov 29, 2006 #2
    Anyone have an idea?
  4. Nov 29, 2006 #3
    well you need an angle because time would depend on the angle you use. For example if you launched the rocket at a 50 degree angle the time to reach its peak would be 58sin50 / 9.81 = 4.42 secs. But if you launched the rocket at a 70 degree angle it would be 58sin70 / 9.81 = 5.55 seconds. So you would have to specify the angle.
  5. Nov 29, 2006 #4
    oh ok, so even if you shoot the firework straight up, it still needs an angle?
  6. Nov 29, 2006 #5
    well straight up it would be 90 degrees. 58sin 90 / 9.81 = 5.912 seconds.
  7. Nov 29, 2006 #6


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