Question

When a knife is sharpened with the help of a rotating grinding stone then the spark always travels tangentially to it, why?

Answer 1

1. If a particle travels in a circular motion, then the direction of the velocity of the particle is tangential.
2. Suppose the grinding stone is rotating, it will have a circular motion. So, the spark travels tangentially.
3. Thus, when a knife is sharpened with the help of a rotating grinding stone then the spark always travels tangentially to it.