Troubleshooting Vectors: Finding Errors in Vector Problems | Help Requested

[elpermic]

vectors problem, help please

Homework Statement

Homework Equations

The Attempt at a Solution

I used the pythagorem theorem on the first two vectors and named it vector x. It turned out to be 4.8km and I used vector x plus 3.1km of the other vector. I got 7.9km at 45 degrees NE. The book says it should be 7.8km at 38 degrees NE. What did I do wrong? OR is it the book>

 

[Feldoh]

Is the resultant vector from 2.6km north and 4.0km east at a 45 degree angle from east?

If not you can't simply add 4.8km to 3.1km because they won't be in the same direction.

 

[rl.bhat]

4.8 km and 3.1 km are not in the same line.
Find the angle between them.
It is equal to (45 degrees - angle between 4 km and 4.8 km.)

 

[elpermic]

Aren't both lines( vector x and the 3.1km vector both going north east?

 

[rl.bhat]

No. It is not. Draw the scale diagram and verify.

 

[ideasrule]

Aren't both lines( vector x and the 3.1km vector both going north east?

Well, you went north 2.6 km, then east 4 km. To have a 45-degree angle, those two values have to be equal, which they aren't.