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Homework Help: What is the kinetic energy of the object

  1. Sep 28, 2004 #1
    Hey can someone check if i did it right please. Thanks




    At t= 1.0 secs, a 0.40-kg object is falling with a speed of 6.0m/s. At t= 2.0 secs, it has a kinetic energy of 25J. (a) What is the kinetic energy of the object at t= 1.0 secs? (b) What is the speed of the object at t = 2.0 secs? (c) How much work was done on the object between t= 1.0 secs and t= 2.0 secs?

    (a) k= (1/2)mv^2
    =(1/2)(.40kg)(6.0m/s)^2
    = 7.2J

    (b) k= (1/2)mv^2
    25J = (1/2)(.40kg)(m/s)^2
    50J = (.40kg)(m/s)^2
    =(125)^(1/2)
    = 11.1803m/s

    (c) w= (1/2)m11.2^2-(1/2)m6.0^2
    =(1/2)m5.2^2
    =(1/2)(.40kg)(5.2)^2
    =5.36718J
     
  2. jcsd
  3. Sep 28, 2004 #2

    Pyrrhus

    User Avatar
    Homework Helper

    The concept is fine, i didn't check arithmetic.
     
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