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Use Your Knowledge of English: 

If the sun is 93,000,000 miles from the Earth, how many minutes does it take for sunlight to reach the Earth?
(Given: The velocity of light is 186,000 miles per second.)

_???__minutes = 93,000,000 miles

1. From the Problem write down all the Equivalent Relationships given or Unit Factors.    For example:
2. Beware of our Tricks!


  • We stick extra information in the form of numbers and equivalent relationship you will not need to solve the problem

    The only unit factor left out is 60 seconds = 1 minute

    two step dimensional analysis sequence



    3. Formulate a road map which connects the unit of the given to the unit of the answer by equivalent relationships.

    This takes two unit factors:

    1. First convert miles to seconds using the velocity of light;
    186,000 miles traveled = 1 second of elapse time.

    2. The convert to total seconds for light to reach the earth from the sun
    to minutes by using the unit factor: 60 seconds = 1 minute.

    The Solution:

    Setup the dimensional analysis sequence and solve:

     
      ??? min = 93,000,000 mi X 1 sec X 1 min = 8.33 min  
    1 1 186,000 mi 60 sec 1