What will cause changes in the speed or direction of an object's motion?

Unbalanced forces are responsible for changes in the speed or direction of an object's motion. When forces exerted on an object are unequal, the object will experience acceleration, which can result in an increase or decrease in speed or a change in direction. This is consistent with Newton's second law of motion, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Balanced forces, on the other hand, do not change an object's motion. When forces are balanced, they cancel each other out, resulting in no net force and thus no change in speed or direction. Mechanical waves and visible sunlight do not directly cause changes in the speed or direction of motion in the context of forces acting on an object. Instead, they pertain to energy transfer and electromagnetic radiation, respectively, without affecting the motion described by classical mechanics.