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Determining the time it takes to reach half of a penny's terminal speed

  1. Mar 21, 2009 #1
    The question is:
    The terminal speed of a penny is 11 m/s. By neglecting air resistance, calculate how long it takes for a penny falling from rest to reach half of this speed

    2. Relevant equations
    I thought maybe you had to use one of the kinematic equations but that didnt work

    3. The attempt at a solution
    I tried Vf-Vi/a = delta T
    Also, I tried dividing 11 m/s by gravity and that didnt work.
    Im not sure if I am totally missing an equation needed or if I am making this way harder than it really is. Any help would be greatly appreciated!
  2. jcsd
  3. Mar 22, 2009 #2
    you are on track with the answer, but why use 11ms-1? (as you stated earlier that it was the terminal velocity, and you were going to use half of the terminal velocity.

    Also, the equation does not need to be so complicated. Look at these ones, and figure out which one is needed, by knowing the data you have and the what is in the equations.
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