Example: Identify the force couples that are equivalent. All forces shown are acting in the same plane.

Which of the following is the right answer?:

1. a and b
2. a and c
3. a and d
4. b and c
5. b and d
6. c and d

Answer to Example: Two forces are equivalent only if the resulting couple moments have the same magnitude and direction.

The correct answer is

1. a and b
2. a and c
3. a and d
4. b and c
5. b and d
6. c and d