how does newtons first law explain the motion of an object in the absence of external forces
Newton's first law of motion states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. In other words, if there are no external forces acting on an object, it will either remain stationary or, if already in motion, continue moving at a constant velocity.
If an object is at rest, there is no external force acting on it to cause it to move. Therefore, it will remain stationary until a force is applied to it.
If an object is already in motion and there are no external forces acting on it, it will continue moving in a straight line at a constant speed. This is because no force is acting to slow it down, speed it up, or change its direction.
This concept is often referred to as the principle of inertia. Objects tend to resist changes in their state of motion. They will keep moving in the same direction and at the same speed unless forces are applied to change that motion.
However, it is important to note that even though an object may appear to be at rest or moving at a constant speed, there are often microscopic forces acting on it, such as friction or air resistance. These forces may not be readily noticeable but can still have an impact on the object's motion.