Friction produces heat due to the conversion of mechanical energy into thermal energy. When two surfaces come into contact and slide or rub against each other, the irregularities on their surfaces interlock and create resistance, known as friction. As a result, the objects experience a force opposing their motion.
As the surfaces interact, the friction force causes microscopic deformations, vibrations, and molecular interactions between the materials involved. These interactions result in the conversion of kinetic energy (associated with the motion of the objects) into thermal energy (associated with the random motion of particles at the microscopic level).
The mechanical energy of the objects is dissipated in the form of heat, leading to an increase in temperature. This is why you may feel an object becoming warmer when it is rubbed or when there is relative motion between two surfaces in contact.
The amount of heat generated due to friction depends on various factors, including the nature of the materials, the roughness of the surfaces, the applied force, and the duration of contact. In some cases, excessive friction and heat can lead to wear and damage to the surfaces involved. However, friction and the resulting heat can also be intentionally harnessed for various applications, such as generating fire by rubbing two sticks together or stopping the motion of a vehicle using brake pads.