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Homework Help: Finding the weight, work, and normal force of a block

  1. Sep 18, 2011 #1
    1. The problem statement, all variables and given/known data
    4 questions:
    1. A block of mass M=2.6 kg is dragged over a horizontal surface by a force F=22.0 N. The block is displaced a distance d=10.0 m, the friction force Ff is 3.1 N. What is the weight of the block in Newtons? Use 10 m/s2 for g.

    2. A block of mass M=1.0 kg is dragged over a horizontal surface by a force F=20.0N. The block is displaced a distance d=10.0 m, the friction force Ff is 5.0 N. What is the work done by the weight Fg?

    3. A block of mass M=2.6 kg is dragged over a horizontal surface by a force F=22.0 N. The block is displaced a distance d=10.0 m, the friction force Ff is 3.1 N. What is the normal force acting on the block?

    4. A block of mass M=3.3 kg is dragged over a horizontal surface by a force F=29.0 N. The block is displaced a distance d=17.0 m, the friction force Ff is 4.8 N. What is the work done by the normal force FN?


    2. Relevant equations

    W=fxd


    3. The attempt at a solution

    I have tried to watch my instructors videos and none of this section makes any sense to me! I am in need of someone to explain how to figure all of these out please !
    Thank you so much
     
  2. jcsd
  3. Sep 18, 2011 #2
    Hi,
    The fundamental thing to remember here, is Newton's second law, or F=ma(mass times acceleration).
    Weight is a special case of a force, where the acceleration is a constant g, and it is always downward, depending on your choice of axes.
    You wrote down correctly, that [itex] \large W = Fd [/itex], but remember that it's a vector product, a dot product, and preferably an integral, [itex] W = \displaystyle \int \vec{F}\cdot d\vec{r} [/itex].
    Does this make things clearer?
    Daniel
     
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