# Need Help.

1. Aug 28, 2007

### AraProdieur

Four vectors, each of magnitude 62 m, lie along the sides of a parallelogram as shown in the figure. The angle between vector A and B is 49 degrees.
What is the magnitude of the vector sum of the four vectors? Answer in units of m.

So far, I have drawn the picture and made out with a parallelogram with the left side as vector A, the top vector C, the right vector D, and the bottom vector B with all of the sides congruent to each other respective to 62 m, and also the angle with between vector A and B is 49 degrees which also means that between C and D is the same while between both A and C and B and D is 131 degrees in between.

What I've been thinking was since I have to find the magnitude of the vector sum of the four vectors, wouldn't it be the same as finding the magnitude diagonal of the parallelogram? or am I off the tee here?

2. Aug 29, 2007

### Staff: Mentor

Can you post a link to the figure, or uplink it as an attachment? We'd like to help, but we need the figure. Thanks.

3. Aug 29, 2007

### Astronuc

Staff Emeritus
If A and C point in the same direction (parallel), they are additive, otherwise if anti-parallel they cancel. Similarly for B and D.

If the head (point) of A touches the tail of B, then they are additive, and resultant is the diagonal. If the point of B touches the tail of C, then C is in the opposite direction of A, and their contributions to the vector sum cancel.

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