When do we use dot product and when do we use cross product?

Question

I actually dont understand that when do we use cross product and when to use dot product ……it is very difficult to remember that a torque is cross product and work done is dot product. please tell me the reasons behind these so that i can understand the concept not just blindly memorize?

Answer 1

The cross product's output is a vector and it tells you how much of the two vectors are at right angles to each other. The cross product of parallel vectors is zero. The cross product of two perpendicular vectors is another vector in the direction perpendicular to both of them with the magnitude of both vectors multiplied.

The dot product's output is a number (scalar) and it tells you how much the two vectors are in parallel to each other. The dot product of two parallel vectors is the product of their lengths. The dot product of two vectors at right angles to each other is zero.