What is the cause of motion according to fundamental physics?

In fundamental physics, the cause of motion is identified as force. According to Newton's second law of motion, force is defined as the product of mass and acceleration (F = ma). This indicates that it is force that causes an object to change its state of motion, whether that be moving from rest to motion, altering its speed, or changing direction.

While acceleration, velocity, and friction are all connected to the concept of motion, they do not serve as the primary cause. Acceleration is a change in velocity, which results from applying a force, thus making it a consequence rather than a cause. Velocity describes the speed and direction of an object in motion, but it does not instigate that motion. Friction is a force that opposes the motion between surfaces in contact; therefore, while it can affect how motion occurs, it does not cause motion to happen on its own.

Overall, understanding that force is the initiating factor behind motion is foundational in physics and essential for analyzing various physical systems.