# Vector Help. Calc based Physics 1

1. Jan 21, 2008

### dukebdx12

1. The problem statement, all variables and given/known data

Rank from largest to smallest:
2i+7j-4k , 3i+j-k , 7i - 2j +4k , 4i + 7j - 3k

2. Relevant equations

3. The attempt at a solution
Don't understand how and what to look for

1. The problem statement, all variables and given/known data

A receiver starts at +2i - 3j with the units being expressed in yards. i is the the right and j is downfield. The receiver goes +9.0i +12j , -6i +4.0j , +12.0i + 18j and the quarterback drops back -7.0j.
How far must the quarterback throw the ball?
In which direction must the quarterback throw the ball? In degrees

2. Relevant equations

3. The attempt at a solution
I have drawn it and the 2 answers I came up with are 41 and 38 yards. Neither are right. I don't know how to find the angle.

1. The problem statement, all variables and given/known data
Ax = +5.7 Bx = -9.8
Ay = -3.6 By = -6.5

The magnitude of the vector difference , is closest to:
16,11,250

3. The attempt at a solution
I have tried 5 and -5 and right now looking at my paper I forgot the equation I used but it must have been wrong

Last edited: Jan 21, 2008
2. Jan 21, 2008

### Shooting Star

Q1. These are vectors. Vectors have magnitudes and directions. On what basis do you think they should be arranged?

Q2. Vector displacement of ball = Recvr's posn vector - Qbacks's posn vector. How do you find the magnitude and angle with the, say x-axis, of a Cartesian vector?

Q3. Vector A = Axi + Ayj etc. Subtract and find the magnitude of the resulting vector.

3. Jan 21, 2008

### Feldoh

Q1. $$|v| = \sqrt{x^2+y^2+z^2}$$ It's fairly easy to prove if you don't believe me.