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Magnitude of the net force

  1. Oct 6, 2009 #1
    A 3.40 kilogram mass is moving in a plane, with its x and y coordinates given by x = 4.85t2 - 1.05 and y = 3.25t3 + 2.10, where x and y are in meters and t is in seconds. Calculate the magnitude of the net force acting on this mass at t = 2.10 seconds.



    I dont know if im supposed to plug in 2.10 for t at the begining because i got a relativly different answer when i tried that
     
  2. jcsd
  3. Oct 6, 2009 #2

    rl.bhat

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    To find the force on the mass, first of all you have to find the acceleration of the mass.
    Find ax = d^2x/dt^2 and ay = d^2y/dt^2 at given time t. Find net acceleration and then the net force.
     
  4. Oct 6, 2009 #3
    So i find the derrivative of the x and y then plug in t=2.10?
     
  5. Oct 6, 2009 #4

    rl.bhat

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    Yes. Find the derivative twice to get the acceleration.
     
  6. Oct 6, 2009 #5
    i see thanks
     
  7. Oct 8, 2009 #6
    After that i take the sum of the accelerations at 2.10 multiplied by the mass 3.40?
     
  8. Oct 8, 2009 #7

    rl.bhat

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    To find the net acceleration you have to find the vector sum of ax and ay.
     
  9. Oct 8, 2009 #8
    i found that to be 9.7+ 40.95=50.65. do i take 50.65 multiplied by 3.40kg's to get the answer of the net force in newtons?
     
  10. Oct 8, 2009 #9

    rl.bhat

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    ax and ay are perpendicular to each other. You can't add then directly to get the resultant acceleration.
     
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