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Unformatted text preview: 1.8 The Component Method of Vector Addition any times using Law of Sines or Law of Cosines will work when doing Many times, using Law of Sines or Law of Cosines will work when doing vector addition. However, there are times when the geometry can get complicated, and a etter way presents itself. better way presents itself. This is the component method of vector addition . It works every time and for any number of vectors. Let’s say I have two vectors A and B , and I know the resultant vector C , such that C = A + B . → → → → → → Let’s say the vectors are in the xyplane and they look like the following: y B → C → x A → y Let’s go ahead and break A and B down into their x and ycomponents. → → → B → C → B y → → Now let’s add the x and ycomponents of ector the plot → C y → x A A x → A y → B x vector C to the plot. C x → → Now it’s easy to see that A x + B x = C x and A y + B y = C y → → → → → y y → → → C A y → B y C y → C ⇒ x A x → B x → C x → x Once you have the two components of vector C , then how do you calculate its magnitude??? → Use the Pythagorean Theorem!!! C 2 = C x 2 + C y 2 Remember, this method works for any number of vectors, so in general, given n vectors, the scalar components of the resultant vector R x and R y will be: R x = A x + B x +C x + D x + · · · + n x A B C D + n R y = A y + B y +C y + D y + · · · + n y nce the scalar components R nd R re calculated then the magnitude Once the scalar components R x and R y are calculated, then the magnitude of R is found by Pythagorean Theorem. R 2 = R 2 + R 2 x y Example: Staggering out of Fred’s at 2 AM on a Friday night, you can’t remember where you parked your car. From the bar door you walk 30 m due north, stop, and walk 10 m due east. Here you stop again and then walk 15 m at 30 o south of east. Finally you reach your car. What is the magnitude and direction of the resultant vector (called your displacement vector)? Give the direction relative to east. y, north B = 10 m 30 o The resultant vector, R , would then be: Notice that the following vector equation would be correct: A = 30 m R = → → → → Car x, east R A + B + C So how do I find the magnitude f ?? → Fred’s of R ???...
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This note was uploaded on 09/25/2011 for the course PHYS 2002 taught by Professor Blackmon during the Spring '08 term at LSU.
 Spring '08
 BLACKMON
 Physics, Work

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