A free particle in physics refers to a particle that is not subject to any external forces. This means that the motion of the particle is not affected by any other objects or forces in its surroundings.
The concept of a free particle is closely related to Newton's first law of motion, also known as the law of inertia. This law states that an object will remain at rest or continue to move at a constant velocity unless acted upon by an external force. A free particle, by definition, is not subject to any external forces and therefore follows this law.
In classical physics, a free particle is a theoretical concept used to simplify calculations and understand the behavior of particles in certain situations. However, in reality, all objects are subject to some form of external forces, such as gravity or air resistance. Therefore, a truly free particle does not exist in reality.
One common misconception about free particles is that they have no mass. However, a free particle can have mass and still be subject to no external forces. Another misconception is that free particles are always in motion. In reality, a free particle can be at rest if it is not acted upon by any forces.
In quantum mechanics, free particles are described by wave functions that represent the probability of finding the particle in a certain location or state. Unlike classical physics, where the position and velocity of a particle can be known with certainty, the behavior of free particles in quantum mechanics is described by probabilities and uncertainties.