Hi again

[Baby Einstein]

Hey guys, boggled again :confused: need some help. And by the way, thanks to everyone who helped out on the last question...much appreciated!

Combine the following two vectors to find the resultant vector.

Vector A = 7.4 units at 30 degrees and Vector B = 11.1 units at 120 degrees

A. Resulant = 13.34 units ; angle = 86.3 degrees
B. Resulant = 18.49 units; angle = 60.0 degrees
C. Resulant = 17.89 units, angle = 48.1 degrees
D. Resulant = 17.89 units; angle = 41.9 degrees


the only thing I can figure is that using the Pythagoryn Therom is that 7.4 and 11.1 comes out to 13.34 but I cant figure the math on how to get the angle to match up. thats asuming that 13.34 is a correct figure

:surprised

[Baby Einstein]

Ok...using a vector calculator at http://hyperphysics.phy-astr.gsu.ed.../vect.html#vec7 I figured out that "A" is the correct answer. So using the Pyth therom is the right way to start

But I still dont know how to do the math on the angle.

[Tide]

Find the x and y components of each vector, add them together to find the resultant vector and the ratio of the y to x components of the resultant vector is the tangent of the desired angle.

[Alkatran]

The trick with vectors is to see them as triangles. You draw the vectors out (in the correct direction! VERY important!) then put the x and y components on them to form a triangle.

Then you start solving the triangles... add their x and ys respectively and recombine the summed values using pythagoras to get the resultant.

[Baby Einstein]

sine Alpha=11.1/13.34=.832 giving Alpha=56.3degrees. Adding vector A's
30degrees to Alpha gives the total angle of 86.3degrees

Thanks again :blushing: