HI I m attempting chp 1, problem 46: The three displacement vectors in the drawing have magnitudes of A = 4.14 m, B = 5.51 m, and C = 3.36 m. Find the resultant ((a) magnitude and (b) directional ang

asked by @freddiet1 • over 1 year ago • Physics • 5 pts

le) of the three vectors by means of the component method. Express the directional angle as an angle above the positive or negative x axis. got 1.52m -65 deg. what am i doing wrong?

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2 answers

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I did: Ay= 4.14sin20=1.42 Ax=4.14cos 20= -3.89 By=5.51 sin 60= 4.77 Bx= 5.51 cos 60 = 2.58 Cx=0; Cy=-3.36

Ry=1.42+4.77+-3.36=2.83 Rx=-3.89+2.58+0=-1.31 R=sqrt of 2.83^2 + -1.31^2=3.12 arctan 2.83/-1.31= -65

answered by @freddiet1 • over 1 year ago

Hi Freddie. It seems you are doing everything right. However, you are expressing your angle as -65 when the problem wants it in terms of the direction in relation to the positive or negative x-axis. If we draw our resulting vector R we see its pointing in the second quadrant (between 90 and 180 degrees in a unit circle). This means we are in negative x territory and our angle points above the x-axis. Therefore, when calculating the angle disregard the negative and deal with magnitudes only. Also, I believe you made a slight miscalculation. For Bx, I got 2.76 not 2.58. This changes the answers slightly to R=3.05 and theta=68. Let me know if this is correct and if you have other questions :)

answered by @juanv2 • over 1 year ago