Vector A has a magnitude of 5.00 units, vector has a magnitude of 5.00 units, and the dot product A·B has a value of 16. What is the angle between the directions of A and ?

Answer 1

A•B= |A||B| cosα
cosα =A•B/ |A||B|=
=16/5•5=0.64
α=cos⁻¹α=50.2°

Answer 2

A person walks in the following pattern: 2.8 km north, then 2.7 km west, and finally 6.9 km south. Construct the vector diagram that represents this motion and from it judge how far and in what direction a bird would fly in a straight line from the same starting point to the same final point. (Choose east as the +x direction.)