What is force?

Force is defined as an interaction that, when unopposed, changes the motion of an object. This includes starting an object's movement, stopping it, changing its direction, or altering its speed. In physics, force is a vector quantity, which means it has both magnitude and direction. The concept of force is essential in understanding dynamics and motion, as articulated in Newton's laws of motion.

The other choices do not accurately represent the definition of force. The measure of mass pertains to the quantity of matter in an object and does not convey any information about the effects of this matter on motion. The speed of an object refers to how fast it is moving, which is unrelated to the ability of forces to change that motion. A static state of an object indicates that it is at rest, which does not involve any force acting on it to cause a change in motion. Therefore, the accurate characterization of force is that it causes changes in the motion of an object, making the first choice the correct answer.