Chapter 12 - Vectors and the Geometry of Space - 12.4 The Cross Product - 12.4 Exercises - Page 862: 40

(a) 40 ft-lb (b) 12 ft-lb

(a) Arm: $i+2j$ ft Force: $20 i$ lb $A \times F =-40 k$ $|A \times F|= $|$i+2j$||$20 i$|$=40 ft-lb$ (b) Arm: $0.6i+0.6j$ ft Force: $20 i$ lb $A \times F =-12 k$ $|A \times F|= $|$i+2j$||$20 i$|$=12 ft-lb$