What do we call equal forces acting on an object in opposite directions?

Equal forces acting on an object in opposite directions are termed balanced forces. This concept is central to understanding the dynamics of objects in motion. When balanced forces act on an object, they cancel each other out, resulting in a state of equilibrium. This means that if the object is at rest, it will remain at rest, and if it is already in motion, it will continue to move at a constant velocity in a straight line.

Balanced forces are crucial in various scenarios, such as when a book lies still on a table or when a car moves at a steady speed on a flat road. In both cases, the forces acting upon the objects maintain their state of motion without causing any acceleration.

The other terms—adjustable forces, unbalanced forces, and net forces—describe different dynamics. Adjustable forces refer to forces that can change magnitude or direction, unbalanced forces lead to acceleration and a change in an object's motion, and net forces refer to the resultant force after all acting forces are considered. However, none of these accurately define the condition of forces that are equal and opposite, which is why balanced forces is the correct term in this context.