We need force to move objects because of the fundamental physical principles of inertia and Newton’s laws of motion.

Inertia is the tendency of an object to resist changes in its state of motion. An object at rest will remain at rest, and an object in motion will continue moving at a constant velocity, unless acted upon by an external force.

This is described by Newton’s first law, also known as the law of inertia. It states that an object will maintain its state of rest or uniform motion in a straight line unless compelled to change that state by an applied force.

Newton’s second law then tells us that the acceleration of an object is directly proportional to the net force acting on it, and inversely proportional to its mass. Mathematically, this is expressed as:

F = m * a

Where:

F = the net force acting on the object

m = the mass of the object

a = the acceleration of the object

So in order to change the motion of an object, whether it’s starting it from rest, changing its speed, or altering its direction, we need to apply a force strong enough to overcome the object’s inertia and accelerate it. The greater the mass of the object, the greater the force required.

Without the application of an external force, objects would simply remain at rest or continue moving at a constant velocity forever, due to inertia. The need to apply force is a fundamental part of how the physical world operates according to the laws of motion.