Question

Where to use dot product and cross product?

Answer 1

There is no specific rule to determine which one (cross-product or dot product) should be used.

If the quantity you want to find out is a scalar quantity then we use dot product the given vectors to find the resultant scalar quantity. And if the desired resultant is a vector quantity then we use cross product between given vectors to find the result.

Dot product is the projection of one vector in the direction of other vector. Cross product gives the resultant which is mutually perpendicular to the given operated vectors.