Question

A spark is produced when two stones strike against each other. why?

Answer 1

When two stones hit against each other with very high speed, the total energy of the impact gets concentrated at a small spot at the point of contact of the hit. In many such occasions, the energy is sufficient to chip off a tiny and hot mass of the stone carrying enormous amount of energy, thus moving with very high velocity.

This motion in air further heats up the speck due to friction with the atmosphere. This heated particle chemically reacts w