Forces Forming a Couple

Steps:

• Recall that a couple consists of two forces acting on a rigid body to produce pure rotation.
• Identify key properties: forces must be equal in magnitude and opposite in direction, with non-collinear lines of action.
• Compare options to these properties: check direction and magnitude.
• Select the option matching both equal magnitude and opposite direction.

Why B is correct:

• A couple is defined as two equal and opposite parallel forces that create a torque without net force, per Newton's laws of motion.

Why the others are wrong:

• A: Different magnitudes create a net force, not a pure couple.
• C: Same direction with different magnitudes results in net force and translation.
• D: Same direction and equal magnitudes produce pure translation, no rotation.

Final answer: B