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Help on a rather simple physics question

  1. Nov 18, 2013 #1
    1. The problem statement, all variables and given/known data
    Suppose you drop a feather and a steel ball of equal masses (0.014 kg) at the same time from a height of 1.5 m and you are told that the feather hits the floor 3.5 s after the steel ball. Estimate the value of the terminal velocity of the feather in air.

    Estimate the feather's drag coefficient.


    2. Relevant equations

    v=mg/c

    3. The attempt at a solution

    I assumed the drag on the steel ball is negligible. So i used r=vit +.5at^2 to find the time it takes for it reach the ground. I then added 3.5s and used another kinematic equation to find the final velocity or terminal velocity. I then plugged the answer into the above equation to find c. it was wrong
     
  2. jcsd
  3. Nov 18, 2013 #2

    Simon Bridge

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    What does the v-t graph of the feather look like?
    i.e. do the kinematic equations even apply to it's motion?

    Consider: if the air-resistance for the steel ball can be neglected - so it never reaches it's terminal velocity - then what is the case for the feather? How long does it take the feather to reach it's terminal velocity?
     
  4. Nov 18, 2013 #3
    Assume that the feather reaches its terminal velocity instantaneously. How far did it fall? How many seconds did it take to fall this distance? What was its velocity?
     
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