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Net Force

  1. Nov 9, 2004 #1
    Whats the net force of an object going UP an incline? I dont have an applied force, just the velocity, mass, and coeffieciant of friction. I solved for the Force of friction but how do i solve for Fnet? I dont think its
    Fnet = Fg(parralel) - Ffriction cause Fg is still pulling down?
     
  2. jcsd
  3. Nov 9, 2004 #2
    Fnet=Fg(parallel)+Ffriction
     
  4. Nov 9, 2004 #3
    hmm, why? lol
     
  5. Nov 9, 2004 #4
    Frictional force opposes object's motion. what is lol ?
     
  6. Nov 9, 2004 #5
    But isnt Fnet in a way equal to the direction of the object? If its going up the incline how can it be Fg+Ff if Fg is going down? lol = laugh out loud (an internet term i guess you could say :tongue:)
     
  7. Nov 9, 2004 #6
    you said there is no applied upward force. so there are only two forces acting on the object, its weight and the kinetic frictional force. Fnet is not necessary equal to the direction of an object. it is going up the incline because of its kinectic energy, the speed it has. because the fnet is acting downward, this net force will tend to slow it down until it stops and then going downward because the acceleration caused by the net force is opposite in direction with its velocity.
    just like when you pull a moving block on a frictionless table with constant force, the block will slow down until it stops and then it will move in the same direction with your pulling force.
     
  8. Nov 10, 2004 #7
    well you'd have Fnet=Fapplied-Ff-Fg

    where Fg and Ff are determined based on the angle of the incline

    if you know the distance traveled you know the work done by the net force, so assume that the final velocity (i assume that is what you know?) is the result of the total work done by the system.
     
    Last edited: Nov 10, 2004
  9. Nov 10, 2004 #8

    HallsofIvy

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    No, he didn't say there was "no applied upward force", he said "I dont have an applied force". Since he did say the object was going UP the incline there must be some upward force.
    Format: you also said you had "just the velocity". If there is no acceleration then the net force is 0, of course. The upward applied force must be equal to the sum of the friction force and weight of the object but in the opposite direction.
     
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