When a system loses its motion due to friction between two surfaces, the kinetic energy of the system is converted into other forms of energy, primarily heat and sound. This conversion occurs because friction acts as a resistive force that opposes the motion of the system.
Kinetic energy is the energy possessed by an object due to its motion, and it is given by the equation:
KE = (1/2) * m * v^2
Where: KE is the kinetic energy m is the mass of the object v is the velocity of the object
When two surfaces are in contact and there is relative motion between them, the frictional force opposes this motion. As the object slows down, the frictional force does negative work on the object, meaning it transfers energy away from the object. This work done by friction is equal to the negative change in kinetic energy of the system.
As the kinetic energy decreases, it is converted into other forms of energy. The primary form is heat, as the friction between the surfaces generates thermal energy. This energy is a result of the microscopic interactions between the atoms and molecules of the surfaces, which create heat due to increased motion and frictional dissipation.
Additionally, some of the kinetic energy may be converted into sound energy. When two surfaces rub against each other, vibrations are created, producing sound waves. These sound waves carry away a portion of the energy of the system.
Therefore, when a system loses its motion due to friction between two surfaces, the kinetic energy is primarily converted into heat energy and sound energy.