Angle between the positive direction of the x axis and a line tangent to the particle's path












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The position $vec r$ of a particle moving in an xy plane is given by $vec r$ = $(1.00t^3 − 3.00t)i + (8.00 − 9.00t^4)j$, with $vec r$ in meters and $t$ in seconds. In unit-vector notation, calculate the following for $t = 2.10 s$.



What is the angle between the positive direction of the x axis and a line tangent to the particle's path at t = 2.10 s? (counterclockwise from the +x-axis)



Is it asking for a degree based on r, v, or a?



Since it mentioned s, I thought it referred to v. So, I did:



-333.4/10.28 times tan inverse. That got -88.1, then I added 180 degrees since it was in Q4, for 91.76 degrees. It says it's wrong, though.










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    0












    $begingroup$


    The position $vec r$ of a particle moving in an xy plane is given by $vec r$ = $(1.00t^3 − 3.00t)i + (8.00 − 9.00t^4)j$, with $vec r$ in meters and $t$ in seconds. In unit-vector notation, calculate the following for $t = 2.10 s$.



    What is the angle between the positive direction of the x axis and a line tangent to the particle's path at t = 2.10 s? (counterclockwise from the +x-axis)



    Is it asking for a degree based on r, v, or a?



    Since it mentioned s, I thought it referred to v. So, I did:



    -333.4/10.28 times tan inverse. That got -88.1, then I added 180 degrees since it was in Q4, for 91.76 degrees. It says it's wrong, though.










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      The position $vec r$ of a particle moving in an xy plane is given by $vec r$ = $(1.00t^3 − 3.00t)i + (8.00 − 9.00t^4)j$, with $vec r$ in meters and $t$ in seconds. In unit-vector notation, calculate the following for $t = 2.10 s$.



      What is the angle between the positive direction of the x axis and a line tangent to the particle's path at t = 2.10 s? (counterclockwise from the +x-axis)



      Is it asking for a degree based on r, v, or a?



      Since it mentioned s, I thought it referred to v. So, I did:



      -333.4/10.28 times tan inverse. That got -88.1, then I added 180 degrees since it was in Q4, for 91.76 degrees. It says it's wrong, though.










      share|cite|improve this question









      $endgroup$




      The position $vec r$ of a particle moving in an xy plane is given by $vec r$ = $(1.00t^3 − 3.00t)i + (8.00 − 9.00t^4)j$, with $vec r$ in meters and $t$ in seconds. In unit-vector notation, calculate the following for $t = 2.10 s$.



      What is the angle between the positive direction of the x axis and a line tangent to the particle's path at t = 2.10 s? (counterclockwise from the +x-axis)



      Is it asking for a degree based on r, v, or a?



      Since it mentioned s, I thought it referred to v. So, I did:



      -333.4/10.28 times tan inverse. That got -88.1, then I added 180 degrees since it was in Q4, for 91.76 degrees. It says it's wrong, though.







      physics






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      asked Sep 24 '16 at 4:05









      user366783user366783

      3829




      3829






















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          $begingroup$

          "Direction" refers to velocity. So calculate the derivative vector at time $t=2.1$ seconds.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            So I should do -333.3/10.28? I already tried that.
            $endgroup$
            – user366783
            Sep 24 '16 at 4:38












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          1 Answer
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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          0












          $begingroup$

          "Direction" refers to velocity. So calculate the derivative vector at time $t=2.1$ seconds.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            So I should do -333.3/10.28? I already tried that.
            $endgroup$
            – user366783
            Sep 24 '16 at 4:38
















          0












          $begingroup$

          "Direction" refers to velocity. So calculate the derivative vector at time $t=2.1$ seconds.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            So I should do -333.3/10.28? I already tried that.
            $endgroup$
            – user366783
            Sep 24 '16 at 4:38














          0












          0








          0





          $begingroup$

          "Direction" refers to velocity. So calculate the derivative vector at time $t=2.1$ seconds.






          share|cite|improve this answer









          $endgroup$



          "Direction" refers to velocity. So calculate the derivative vector at time $t=2.1$ seconds.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Sep 24 '16 at 4:10









          bubbabubba

          30.7k33188




          30.7k33188












          • $begingroup$
            So I should do -333.3/10.28? I already tried that.
            $endgroup$
            – user366783
            Sep 24 '16 at 4:38


















          • $begingroup$
            So I should do -333.3/10.28? I already tried that.
            $endgroup$
            – user366783
            Sep 24 '16 at 4:38
















          $begingroup$
          So I should do -333.3/10.28? I already tried that.
          $endgroup$
          – user366783
          Sep 24 '16 at 4:38




          $begingroup$
          So I should do -333.3/10.28? I already tried that.
          $endgroup$
          – user366783
          Sep 24 '16 at 4:38


















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