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Homework Help: Work And Power Problems Using Inclined Planes and Forces

  1. Feb 23, 2010 #1
    1. The problem statement, all variables and given/known data
    A)What is the minimum work needed to push a 1610 kg car 302 m up a 15 deg incline? Ignore friction.
    B) Assume the effective coefficient of friction is 0.25.

    (I have part A, the answer is 1.23x10^6 J)


    2. Relevant equations
    Force of Friction = [tex]\mu[/tex] x Normal Force
    Work = Applied Force x cos([tex]\theta[/tex]) x distance


    3. The attempt at a solution
    http://i48.tinypic.com/2eg7mlc.jpg"

    -----------------------------------------------------------------------

    1. The problem statement, all variables and given/known data
    A)A grocery cart with mass of 16.3 kg is pushed at constant speed along an aisle by a force of 10.4 N. The applied force acts at a(n) 22.3 deg angle to the horizontal. Find the work done by the applied force if the aisle is 14.9 m long.
    B) Find the work done by the force of friction.
    C) Find the work done by the normal force.
    D) Find the work done by gravity.

    (I have part A, the answer is 143.37 J)


    2. Relevant equations
    Force of Friction = [tex]\mu[/tex] x Normal Force
    Work = Applied Force x cos([tex]\theta[/tex]) x distance
    Work of Gravity = mass x gravity x height
    Work of Normal Force = Normal Force x cos([tex]\theta[/tex])
    Work of Force of Friction = Force of Friction x distance

    3. The attempt at a solution
    http://i45.tinypic.com/1eqf47.jpg"

    -----------------------------------------------------------------------

    1. The problem statement, all variables and given/known data
    A)A 324-kg piano slides 5.16 m down a 30 deg incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of friction is 0.40. Calculate the force exerted by the man.
    B) Find the work done by the man on the piano.
    C) Find the work done by the force of friction.
    D) Find the work done by gravity.
    E) Find the net work done on the piano.

    (I have part D, the answer is 8192.016 J)


    2. Relevant equations
    Force of Friction = [tex]\mu[/tex] x Normal Force
    Work = Applied Force x cos([tex]\theta[/tex]) x distance
    Work of Gravity = mass x gravity x height
    Work of Normal Force = Normal Force x cos([tex]\theta[/tex])
    Work of Force of Friction = Force of Friction x distance

    3. The attempt at a solution
    http://i46.tinypic.com/2renkuc.jpg"

    -----------------------------------------------------------------------

    I've been working on these problems for two days, nearly seven or eight hours in all, and yet I just can't seem to figure out what to do. I'm very sorry if you're not supposed to put more then one problem in each topic but they all use the same concepts so I thought this would be easiest. Any help someone could offer would be much appreciated! I understand the idea of what is going on and why things are happening, I simply get messed up with all the equations and the x-y tables. Please and thank you very much!

    --beyondtheEND_​
     
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
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