1. Section 2 – Vector operation (1/3)
Chapter 3 – 2D Motion
Section 2 – Vector operation
(1/3)

2. Objectives
O1: Find the resultant of vectors that are in the same direction.
O2: Find the resultant of vectors that are in opposite direction.
O3: Find the resultant of vectors that are at 90 degrees.

3. remember

4. Resultant of parallel vectors
Parallel vectors behave like numbers on a number line.
Add the magnitudes of vectors in the same direction
Subtract the magnitudes of vectors in opposite direction.

5. Resultant = A + B = + 4 + (+9) = + 13

6. So adding vectors that point in the same direction gives a:

7. Resultant = A + B = + 4 + (-9) = 4 – 9 = - 5

8. So adding vectors that point in opposite directions gives a:
Total vector
difference between vectors magnitude
Magnitude
equals
has the same direction as the larger vector
Direction:

10. Jump off the line For vectors that are at 90°:
Use Pythagoras' theorem to determine magnitude.
Use tangent  trigonometric function to determine direction.

11. <First little math> Consider a right triangle (has a 90° angle)

17. so by knowing the “tan” of the angle, you can find the angle by tan-1