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Homework Help: More frustrating force problems, please help

  1. Mar 2, 2008 #1
    More frustrating force problems, please help!!

    1. The problem statement, all variables and given/known data
    1.)A chair of mass 10.1 kg is sitting on the horizontal floor; the floor is not frictionless. You push on the chair with a force of 47.7 N that is directed at an angle of 39.6 degrees below the horizontal and the chair slides along the floor. Calculate the normal force that the floor exerts on the chair

    2.)A 87.7 kg man steps off a platform 2.89 m above the ground. He keeps his legs straight as he falls, but at the moment his feet touch the ground his knees begin to bend, and, treated as a particle, he moves an additional 0.60 m before coming to rest. Treating our rigid legged friend as a particle, what is the average force his feet exert on the ground while he slows down?

    Note: Assume the acceleration while he is slowing down is constant

    2. Relevant equations
    For Question 1
    u nid to find the sum of forces in the x and y directions respectively
    for question 2
    remember gravity

    3. The attempt at a solution
    i drew a free body diagram, i suggest u do d samem maybe there was a flaw in mine.
  2. jcsd
  3. Mar 2, 2008 #2
    For the first question, you dont really need to consider the forces in the x direction. What does your FBD look like for the y directions? This should be enough to sum up the forces.

    For question 2 you need to consider the acceleration thats exerted on the person to make him stop in the given distance, and remember newton's second law.
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