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Force/Newtons law Q help

  1. Jan 9, 2013 #1
    A cyclist is pedaling so that a force of 100N pushes her forward while there are 50N of friction and 50 N of air resistance opposing her movement. What is the net force on the cyclist?
     
  2. jcsd
  3. Jan 9, 2013 #2

    Dick

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    Sounds pretty easy to me. What do you think? That's the important part.
     
  4. Jan 9, 2013 #3
    i think its either 200n or 0n :/
     
  5. Jan 9, 2013 #4

    Dick

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    That's good. So which? 100N forward. I think 'opposing her movement' should tell you which direction the other two are, yes? 'Net force' means you add the forces considering the sign of each one.
     
  6. Jan 9, 2013 #5
    so its 200 n
     
  7. Jan 9, 2013 #6

    Dick

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    Right. If she's moving 20km/hr she'll keep on moving 20km/hr until she stops working and slows down or works harder and speeds up.
     
  8. Jan 9, 2013 #7

    Dick

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    I liked your first answer better. If you call forward positive then the other backward forces are negative. 100N+(-50N)+(-50N)=0N.
     
  9. Jan 9, 2013 #8
    ooooooh ok thanksss!!!!!
     
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