Friction and Heat Generation

Rubbing of hands together in winters causes a sensation of warmth mainly because of the heat caused by the force of friction. When two surfaces are rubbed against each other, a force called friction is generated. Friction is the resistance to motion between two objects in contact with each other.

Friction and Heat Production

Friction converts mechanical energy into thermal energy, resulting in the generation of heat. This is known as the heat of friction. When we rub our hands together, the friction between the surfaces of our hands generates heat due to the resistance encountered during the rubbing motion.

Explanation of the Answer

The correct answer, option 'A', states that the sensation of warmth is caused by the heat generated by the force of friction. This answer is accurate because the rubbing motion between the hands creates friction, which in turn produces heat.

Friction and Molecular Activity

The heat generated by friction is a result of the increased molecular activity within the substances being rubbed. When two surfaces come into contact and rub against each other, the irregularities on the surfaces interlock and resist motion. This resistance causes the molecules in the surfaces to vibrate and collide, leading to an increase in kinetic energy and the generation of heat.

Thermal Energy Transfer

As the rubbing motion continues, the heat generated due to friction is transferred from the surface of one hand to the other. This transfer of thermal energy occurs through conduction, where heat flows from a region of higher temperature (the hand with more generated heat) to a region of lower temperature (the hand with less generated heat).

Sensation of Warmth

The sensation of warmth is felt as the heat from the friction is conducted to the skin. The increased temperature of the skin stimulates the nerve endings, which then send signals to the brain, resulting in the perception of warmth.

In conclusion, rubbing of hands together in winters causes a sensation of warmth mainly because of the heat generated by the force of friction. The rubbing motion generates friction, which converts mechanical energy into thermal energy, producing heat. This heat is then conducted to the skin, creating a feeling of warmth.