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Nanoseconds and Time for Light to Travel

  1. Jan 26, 2007 #1
    1. The problem statement, all variables and given/known data
    The problem asks how many nanoseconds does it take for light to travel 1km in a vacuu?

    2. Relevant equations
    I know that 1KM is equal to 1000 meters or 10^3. I also know that 1ns is equal to 10^-9s and light travels at about .3m per ns.

    3. The attempt at a solution

    I'm not sure where to start with this problem. I know I have to convert the two givens but im stuck at where to start. I started to think that I could divide the .3m per ns by 10^9 and then multiply it by 10^3. If someone could help me figure out how to start this problem and a push in the right direction that would be highly appreciated. Thanx in advanced.
  2. jcsd
  3. Jan 27, 2007 #2


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    Science Advisor
    Homework Helper

    You probably remember:
    distance = velocity x time


    time = distance/velocity.

    for constant velocity. So use that.
    You can always get the right relation by considering the units on both sides if you don't see it right away.
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