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Simple Force question

  1. Oct 27, 2012 #1
    1.) A duck has a mass of 2.35 kg. As the duck paddles, a force of 0.144 N acts on it in a direction due east. In addition, the current of the water exerts a force of 0.202 N in a direction of 54.5° south of east. When these forces begin to act, the velocity of the duck is 0.130 m/s in a direction due east. Find the magnitude and direction (relative to due east) of the displacement that the duck undergoes in 2.52 s while the forces are acting.

    2.) F=ma
    Kinematics equations

    3.) So, I worked out that the x-component of F2 is 0.117N and added that to 0.144N. I then plugged the answer (0.261N) into the F=ma formula and got a=0.11m/s^2. I then used the equation d=(Vi)t+1/2(a)(t^2) and got d=0.677m.
    Then, I used the x-component of 0.261N and the Y-component of F2(the only y-component) and solved for the angle getting 31.5deg. I subtracted this from 360 to get the answer of 328.5deg relative to due east. My answers came out to be incorrect.
    Please help!
     
  2. jcsd
  3. Oct 27, 2012 #2

    Delphi51

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    Homework Helper

    For the east direction, I agree with your force of .261 N and a = 0.111.
    I used V = Vi + at to get the final velocity of .4099 and then used
    d = Vavg *t = (.13+.4099)/2*2.52 = .6803 m East.
    Very close to your .677 but could that be what is getting you the wrong answer?
     
  4. Oct 27, 2012 #3
    Um, I think that it may be the direction that's getting me the wrong answer. What did you get for that?
     
  5. Oct 27, 2012 #4

    Delphi51

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    Homework Helper

    Finished it now. We are way different on the angle. For the south distance I got about 0.2 m and an angle of less than 20 degrees south of east, which would be more than 340 degrees counterclockwise from east.
     
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