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What is the theoretical minimum force

  1. Nov 9, 2006 #1
    a 82.500 kg student, starts from rest. A constant force acts on him for 37.5m to give him a speed of 97.5 m/s. Use the Work- energy theorem to find the magnitude of the force.

    this is my equation which I'm unsure about
    1. f*s= .5mv^2f - .5mv^2i
    2. f= .5(82.5)(97.5^2)/37.5
    I just want to know if I'm right so far, thanks!

    What is the theoretical minimum force Matt must provide to the handle of his car jack if he moves his jack handle .45 m each time he lifts his 17000 N car .004m?

    I have no idea how to do this one. F=mg?...

    Hideaki Fukuda is in a 475.0kg roller coaster that is poised, motionless, atop a 77.50, hill. How fast will the frictionlest coaster be moving at the top of the next hill, 62.250 m high?
    I don't understand this problem and I have no idea what equation to use.
    help please!
  2. jcsd
  3. Nov 9, 2006 #2


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    Science Advisor
    Homework Helper

    Your first one looks good. For the jack problem, assuming the mahine is ideal and loses no energy, the work output is equal to the work input. For the last one, it is all about conservation of energy. In the absence of friction, the sum of kinetic energy plus gravitational potential energy is constant.
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