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Homework Help: Statement about ball thrown upwards

  1. Oct 10, 2012 #1
    1. The problem statement, all variables and given/known data
    A ball is thrown vertically upwards and air resistance is NOT negligible.Which of the folloiwng statement is incorrect.
    A:At maximum height,acceleration is zero.
    B: Time taken for ball to travel upwards is shorter than time taken to travel down
    C: Distance traveled for upward and downward motion are the same.
    D: Magnitude of acceleration for the upward motion is always greater than 9.81ms-2

    2. Relevant equations

    3. The attempt at a solution
    I choose A instantly as i knew there is acceleration downwards due to gravity.I was right though.
    But i have no clue why D is correct?If a ball is facing air resistance wouldn't it slow down(Net force is pointing towards Earth)?
  2. jcsd
  3. Oct 10, 2012 #2
    so when the ball is going upwards, what are the forces acting on it
  4. Oct 10, 2012 #3
    Resistive force due to air resistance
    Gravitational force due to gravity
  5. Oct 10, 2012 #4
    right, so if there's two forces in the downwards direction, and one of them is gravity, then what can we say about the total force acting on the ball
  6. Oct 11, 2012 #5
    Yes,but won"t it be that total downward force is larger than 9.81ms-2?
    But Option D seems to imply that it is accelerating upward.
  7. Oct 11, 2012 #6
    no it's just asking about the acceleration *during* the upward motion
  8. Oct 11, 2012 #7
    So option D is saying,When it is traveling upwards,net force/acceleration is acting downwards but it's magnitude is larger than 9.81 due to presence of air resistance???
  9. Oct 11, 2012 #8
    that's what D appears to be saying, is that what you think is happening?
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