Question

When the cutting edge of a knife is put against a fast-rotating stone to sharpen it, sparks are seen to fly. Explain the reason.

Answer 1

Friction produces heat. When the knife's cutting edge comes in contact with a fast-rotating stone, heat is generated due to friction among the grinding stone and the knife's cutting edge. As the friction is considerable, a large amount of heat is delivered, and sparks are seen flying while sharpening the knife's cutting edge.

Complete step-by-step solution:
Friction among the grinding stone and the knife's cutting edge generates heat. As the friction is tremendous, a large amount of heat is generated, and we observe sparks flying. When a knife is sharpened by placing it facing a rotating stone, it creates heat. The increment in the speed of the rotating stone energy on the knife also rises, causing it to spark.
The frictional force among the grinding stone's surfaces and the cutting edge of the knife delivers heat. As the force is vast, a large amount of heat is generated, and we observe the lightning sparks flying.
Due to frictional force among the knife and the rotating stone, the metal knife's edge becomes very warm. Moreover, tiny particles of the knife tear apart from the warm edge. Due to extreme heat, the tiny particles burn, which are observed as the spark.
When the knife's cutting edge is put against a high-speed turning stone to sharpen it, sparks are observed to fly because: The friction rises between the knife's edge and the rotating stone. As a consequence, it enhances the knife's temperature and stone. Friction creates heat as the friction is considerable. In this case, the temperature rises to such a level that the sparks are generated.

Note: Frictional Force indicates the force produced by two surfaces that touch and slide toward each other. These forces are affected mainly by the surface composition and quantity of force needing them together. The angle and position of the object influence the volume of frictional force.