According to Newton's Second Law, acceleration is directly proportional to what?

Newton's Second Law of Motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This relationship is expressed mathematically as ( F = ma ), where ( F ) represents the net force, ( m ) is the mass, and ( a ) stands for acceleration.

When a net force is applied to an object, if the force increases, the acceleration of the object will also increase, assuming that the mass remains constant. This principle explains why a heavier object requires a larger force to achieve the same acceleration as a lighter object. Therefore, option B accurately reflects this foundational concept in physics that ties force and acceleration together directly.

The other factors mentioned, such as the object's mass, direction of motion, and initial speed, do not have a direct proportional relationship with acceleration as dictated by Newton's Second Law. While mass affects how much force is required for a certain acceleration, it does not directly relate to how much the acceleration changes for a given force. The direction of motion and initial speed can influence motion but do not directly determine the specific relationship of acceleration as stated in the law.