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Homework Help: Help with air resistance

  1. Jun 23, 2014 #1
    Can someone please explain the math of this problem?

    -If F is the force of air resistance on an object with mass m moving at a constant velocity, which of the following best describes the acceleration of the object when the force of air resistance is reduced by a factor of 4?
    (a) F/m
    (b) 1/2 F/m
    (c) 1/4 F/m
    (d) 3/4 F/m

    The answer is d but I do not understand how to get it. Thanks in advance!!
  2. jcsd
  3. Jun 23, 2014 #2
    If it is moving at a constant velocity, what force is required in order to maintain that velocity in the initial case (with full air resistance)?

    If the Air resistance is reduced by a factor of four, but the same force is assumed to be acting on the object, how does the object react?
  4. Jun 23, 2014 #3
    I am assuming that when velocity is constant, then the F(air) must cancel out the F of (mg). Therefore, when I drew this out on paper, I made the F(mg) component longer and the F(air) shorter since F(air) is reduced.

    How do the fraction come into play? How is the answer 3/4 F/m? Thanks in advance
  5. Jun 23, 2014 #4


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    What is the net force remaining when you reduce the air resistance by a factor of 4?
  6. Jun 23, 2014 #5
    I get it. Reducing by a factor of 4 requires one to think in terms of fractions (1/4). Therefore, the net F remaining is 3/4. Thanks again!
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