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Homework Help: Work and Energy Question

  1. Dec 16, 2014 #1
    1. The problem statement, all variables and given/known data
    A person starts to mow a lawn with 50kg old fashioned push lawn mower. The handle of the mower makes an angle of 45 degrees with the sure of the lawn. A 200 N force is applied along the handle of the mower by the person
    a. Determine the normal force exerted by the ground on the mower
    b. If u=0.2, determine if the mower moves with a constant speed.
    c.How far the mower will travel if the person pushes it for 1min along the staright line?
    2. Relevant equations

    3. The attempt at a solution
    a) Fnormal = 200Nsin45 = 141

    b) F=uFnormal (.2)(141) = 28.2
    F = ma
    112 / 50
    a = 2.24
    c. ?

    Not sure if a or b are correct
  2. jcsd
  3. Dec 16, 2014 #2


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    This (with a unit added in the end) is only accounting for the force necessary to counteract the push that the person exerts on the handle. The lawnmower also has a weight (assuming non-zero gravity).
  4. Dec 16, 2014 #3


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    Is this the only force applied to the ground by the mower?

  5. Dec 17, 2014 #4
    You have the vertical component of the applied force + the weight [Mg] , so what is Fn.
    Use Newton Second Law
    Think about the net force , what will it be?
    Note that there is no motion along the y-axis and don't forget to take the frication into account.
    What is your equation along the x-axis?
    Use the linear motion laws [after getting 'a' from the previous part ]
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