Understanding Moments of Force and Vector Cross Products in Physics

1. READING QUIZ The moment of a force about a point or an axis provides a measure of the force’s tendency ___ A) to move a body towards the point or axis. B) to rotate a body about the point or axis. C) to deform a body. D) to lift a body.

2. READING QUIZ Select the magnitude of the cross product of two vectors A and B that have an inside angle  between them. A) AB sin  B) A sin  B C) AB cos  D) A2 + B2– 2AB cos 

3. A 5” 4” B C 3” F = 10 lb READING QUIZ Find the moment of force F with respect to point C. A) 0 B) 30 inlb C) 40 inlb D) 50 inlb

4. 2’ A Y 3’ F = – 100 k lb CONCEPT QUIZ The moment of vector of force F with respect to point A can be written as Z A) {200 i + 300 j }ft-lb B){– 200 i + 300 j }ft-lb C){– 200 i – 300 j }ft-lb X D){200 i – 300 j }ft-lb

5. 2’ A Y 3’ F = – 100 k lb CONCEPT QUIZ The moment vector of force F with respect to point A lies in the Z A) x-z plane. B)x-y plane. C)y-z plane. X D)Cannot be determined.

6. ATTENTION QUIZ Select the true statement. A) i  i = 1 B) i j= - k C) k  j = – i D) k  i = – j

7. A 5” 4” B C 3” F = 10 lb ATTENTION QUIZ Using the figure, find the moment of force F with respect to point A . A) 0 B) 30 inlb C) 40 inlb D) 50 inlb