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  1. J

    Work, Friction and Direction

    Since friction is in the opposite direction as the direction of movement, wouldn't you expect the work to be negative? When I put it in the work formula, W = F * cos(180O) * d it comes out positive because F is negative and cos(180) is negative too. This means that if I have another force...
  2. J

    Work and friction

    Sorry, I forgot the force: It's 20 Newtons from the dog's mouth (15 degrees form horizontal).
  3. J

    Work and friction

    Homework Statement This is a question about work: There is a dog pulling a sled across a patch of snow *with a force of 20 Newtons*, the dog's mouth is 15 degrees above horizontal and the sled weighs 5Kg. The snow has a coefficient of friction of 0.2, how much work has the dog done once it has...