Question

Consider the vectors shown in Figure 9. Determine the magnitude and direction of A x B for each. A=5 40° 90° B-3 A 2 B 3 A=4 Figure 9: Sets of vectors A and B for which A x B is to be computed geometrically

Answer 1

a) A×B=AB sin(40)=5×3×.64=9.6

b) A×B= AB sin(180)=5×3×0=0

c)A×B=AB sin(90)=5×3×1=15

Direction of A × B in part a and part c is perpendicular to both A and B in part A it is perpendicular to plane of paper and downward .And in part C is perpendicular to plane and upward.

We can find direction by right hand thumb rule .Place your right hand along Vector A and then move four fingers along B ,thumb will give us direction of resultant vector.