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Homework Help: Air Resistance Question

  1. Mar 24, 2014 #1
    1. The problem statement, all variables and given/known data

    If a ball is thrown upwards and lands in the same spot, would it take longer to reach max height or drop back down from the max height? Also use air resistance.

    2. Relevant equations

    3. The attempt at a solution

    I believe that it would take longer for the object to fall back down. I think it is because that when throwing a ball upwards, gravity would be positive and for ex. if a ball was thrown with acceleration of 2m/s^2, you would add two to 9.8 which would help the ball go up faster while when falling down, the ball air resistance would be in the opposite direction causing the ball to fall back slowly. I'm not sure how to explain my answer properly. This is what I understand so far, if I'm not correct can someone please explain this too me.

  2. jcsd
  3. Mar 24, 2014 #2
    You are not correct.

    First of all let's assume air resistance is a function of velocity and it creates a drag force in the opposite direction of motion.

    Second, you can't throw anything with an acceleration once it leaves your hand. You can only accelerate it over the time your hand can continue to exert a force on it. Once it leaves your hand it will only have an initial velocity.

    Do you know the kinematic equations of motion?
    Last edited: Mar 24, 2014
  4. Mar 24, 2014 #3
    Yes. How would you use that when explaining the answer for this question?
  5. Mar 24, 2014 #4


    User Avatar

    Staff: Mentor

    I doubt that you will be able to account for your answer mathematically without resorting to the use of caculus. (By the way, air resistance always acts to oppose the motion.)

    But perhaps you should ponder an extreme example. (Hint: terminal velocity)
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