Vector A has magnitude 8.00 mm and is in the xy-plane at an angle of 127∘ counterclockwise from the +x–axis (37∘ past the +y-axis). The sum A +B is in the −y-direction and has magnitude 12.0 mm. Find the vector B.

Respuesta :

Answer:

-75.35°

Explanation:

Let C be the sum of the two vectors A and B. Hence, we can write the following  

[tex]A_{x} +B_{x} =C_{x} ......(1)\\A_{y} +B_{y} =C_{y} ......(2)[/tex]

but since the vector C is in the -y direction, [tex]C_{x}[/tex]  = 0 and [tex]C_{y}[/tex] = —12 m.  

Thus  

[tex]B_{x} =-A_{x} =-[-Acos(180-127)]=(8)*cos(53)\\B_{x} =4.81m[/tex]

similarly, we can determine [tex]B_{y}[/tex] by rearranging equation (1)  

 [tex]B_{y} =C_{y} -A_{y} =-12m-[(8)*sin(53)\\B_{y} =-18.4m[/tex]

so the magnitude of B is

[tex]B=\sqrt{B_{x}^2+B_{y}^2 } \\B=19m[/tex]

Finally, the direction of B can be calculated as follows  

Ф=[tex]tan^{-1} (\frac{B_{y} }{B_{x} } )\\=-75.35[/tex]

hence the vector B makes an angle of 75.35 clockwise with + x axis