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Homework Help: The diffrent frictions and how they apply in life.

  1. Nov 23, 2009 #1
    Okay, so on this last section we have been learning about friction. I'm a newby and right now we know of kinetic friction, static friction, and rolling friction. So the friction occurring when a person is walking would be kinetic right? Then when a car is braking it would be .. static?
    When a car is accelerating.. Rolling?? I hope I got these right
  2. jcsd
  3. Nov 24, 2009 #2
    Not really Hazzard,

    Static friction is a type of friction that only acts on resting objects, and it is always bigger than kinetic friction..

    (have you ever did calculations in the class about friction force acting on a moving object? if yes say so)

    To make it more clear for you,

    Lets say that we have a box at rest, its mass is 10 kg's and friction coeffecient between the box and the ground is 0.1.So you expect the friction force would be 1 always? (when there is a force acting horizontally).But its not the case, if you push the object with a force of 1.2 N it may* not move because of the static friction, and when it moves after you apply like 1.5 N, friction force would decrease to 1 N (thats kinetic friction)
  4. Nov 24, 2009 #3
    Friction for a person walking is static friction because there is no relative motion between the surfaces. Friction for a breaking car depends on what the car is doing. Most of the time when you are acclerating (or decelerating) it is static friction because there is no relative motion between tires surface and the road surface. If you break and accelerate suddenly and the car skids, it is kinetic friction. If you just let your car coast to a stop, it is rolling friction.
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