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Homework Help: Motion questions

  1. Jun 17, 2004 #1
    Motion questions....

    Need a little help...

    If the sun is a distance of 1.5 x 10^8 km from earth, how long does it take sunlight to reach earth if it moves at 3.0 X 10^8 m/s?

    A rocket moves through out space at 11,000 m/s. At this rate how much time would be required to travel the distance from the Earth to Moon, which is 38,000 Km?

    A rifle is fired straight up, the bullet leaves the rifle with an initial velocity magnitude of 724 m/s. After 5.000 s the velocity is 675 m/s. At what rate is the bullet decelerated?

  2. jcsd
  3. Jun 17, 2004 #2


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    Homework Helper

    speed = distance/time. Use this equation to answer the first two questions (you may have to rearrange it to isolate for different variables). For constant acceleration (or "deceleration") as it is in your case:

    acceleration = (velocity at time2 - velocity at time1)/(time2 -time1)

    and (time2 - time1) is the change in time, or the time elapsed.
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