Equilibrium requires equal and opposite forces

Steps:

• For translational equilibrium, the vector sum of all forces must be zero.
• With two coplanar forces of equal magnitude, they must be equal in magnitude and opposite in direction to cancel out.
• Examine each diagram to check if the forces are collinear and 180 degrees apart.
• Select the diagram where forces point directly toward and away from each other.

Why A is correct:

• Newton's first law states that an object is in equilibrium if the net force is zero; in A, the forces are equal, opposite, and collinear, resulting in zero net force.

Why the others are wrong:

• B: Forces act at an acute angle, producing a nonzero resultant.
• C: Forces are perpendicular, yielding a net force of magnitude √2 times one force.
• D: Forces act in the same direction, doubling the net force.

Final answer: A