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Homework Help: Introductory problem about force (N)

  1. Apr 8, 2015 #1
    1. The problem statement, all variables and given/known data
    A car of mass 1000 kg accelerates on a straight, flat, horizontal road with an acceleration a = 0.3 m s-2 . The driving force F on the car is opposed by a resistive force of 500 N. What is the net (resultant) force on the car?

    2. Relevant equations

    3. The attempt at a solution
    0.3*1000= 300N
    500N- 300N= 200N
    answer is 300N... Why?
    Last edited by a moderator: Apr 8, 2015
  2. jcsd
  3. Apr 8, 2015 #2
    To use Newton's second law, F should be the NET force, the sum of all forces
    F = m*a retry solving the equation ;)
  4. Apr 8, 2015 #3


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    Staff: Mentor

    The 500N number is not needed for this problem -- they just threw that in to confuse you. The Net Force F is what gives the Net Acceleration a with the car having the Mass m. They ask for the Net Force and give you the Net Acceleration and mass. That's all you need. Makes sense now?
  5. Apr 8, 2015 #4
    thanks that helps
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