1. Visit this thread to beta-test StudySchedule.org. StudySchedule is a free nonprofit site that builds dynamic MCAT study schedules unique for your needs and timeline.
Hey, Guest, do you know how much will it cost you to apply to medical school? Check out SDN's Medical School Application Cost Calculator and plan your budget.

Flea Jumping Problem

Discussion in 'MCAT Study Question Q&A' started by sniderwes, May 21, 2014.

  1. SDN is made possible through member donations, sponsorships, and our volunteers. Learn about SDN's nonprofit mission.
  1. sniderwes

    sniderwes 2+ Year Member

    116
    25
    Jan 18, 2014
    Hey, here's the problem-A 1 mg flea can jump to a height of .2m. The length of its leg is .5mm.
    What is the approximate force F a flea exerts on the ground during a jump?
    a) 2*10^07
    b)1*10^-5
    c)4*10^-3
    d) Can't be determined

    I said d because you don't know how long the leg is exerting the force for, so you don't know what velocity it is launched with (since you don't know impulse).
    However this seems to be going in the completely wrong direction.

    Their answer was just mgh=Fd, where d is the length of the leg. How does this make sense physically? I don't get how you know the leg will be exerting the force for its full length...like if a person is standing upright and they jump, their legs only exert force for a little bit until they leave the ground. Are you supposed to assuming their legs are crumpled to the ground before jumping?
     
  2. SDN Members don't see this ad. About the ads.
  3. tdod

    tdod 5+ Year Member

    217
    19
    Oct 30, 2011
    you are right, they make an assumption that the flea's leg will exert a force for the distance of its leg. i am not an entomologist, so i can't tell you whether or not that is a good assumption. it's a flawed question in my opinion.
     
  4. DrknoSDN

    DrknoSDN

    450
    104
    Feb 21, 2014
    Only suggestion I might have is look for trigger words in the question. "What is the approximate" would make you think you are intended to make an approximation based on an equation if at all possible. Thus you would need to know what equation they want you to plug and chug. Check if all the variable required are given and approximate it.

    You should only choose "can't be determined" if you know what equation is required to make the approximation, and also that they did not give you all the variables required to perform the calculation.
    If it truly can't be determined it should be somewhat obvious because they are asking you specifically about an equation you are supposed to memorize. And the MCAT is usually more focused on your ability to reason.

    This question was probably just related to the current scientific news of 2011, so it may not be the most intuitive because prior to that, "how a flea jumps" was debated.
    http://www.npr.org/2011/02/10/133602679/itching-to-know-how-fleas-flee-mystery-solved
     

Share This Page