Topic: Engineering Mechanics
If a number of forces act on a rigid body, each force may be replaced by an equal and parallel force acting through a fixed point, together with a couple. For the rigid body to be in equilibrium.
- A. Both resultant force and couple must zero
- B. The resultant couple on the body must be zero
- C. The resultant force at the fixed point must be zero
- D. None of the above
Answer: A. Both resultant force and couple must zero
Explanation: If a number of forces act on a rigid body, each force may be replaced by an equal and parallel force acting through a fixed point, together with a couple. For the rigid body to be in static equilibrium, both the resultant force ($\Sigma F_{R} = 0$) and the resultant couple ($\Sigma C = 0$) must be zero.