# Having trouble understanding a question - vector or scalar or neither

• Jun 8th 2010, 04:57 AM
Kakariki
Having trouble understanding a question - vector or scalar or neither
Hey!
I am having trouble understanding what this question is answering, and also how to go about answering it! Hopefully some help can be derived from this thread.

Question
Explain where the quantity $\displaystyle \frac{a \bullet b + a \bullet a \times b}{|b|}$ is a vector, scalar, or neither. Explain your answer.

Solution
I don't understand what this question is asking. I know how to tell if something is a scalar or vector quantity (for example the wind blowing at 20km/h is scalar, but the wind blowing at 20km/h going NW is a vector) but I don't know how to apply it to this question!
I also know how to calculate the cross and dot products.

• Jun 8th 2010, 05:03 AM
AllanCuz
Quote:

Originally Posted by Kakariki
Hey!
I am having trouble understanding what this question is answering, and also how to go about answering it! Hopefully some help can be derived from this thread.

Question
Explain where the quantity $\displaystyle \frac{a \bullet b + a \bullet a \times b}{|b|}$ is a vector, scalar, or neither. Explain your answer.

Solution
I don't understand what this question is asking. I know how to tell if something is a scalar or vector quantity (for example the wind blowing at 20km/h is scalar, but the wind blowing at 20km/h going NW is a vector) but I don't know how to apply it to this question!
I also know how to calculate the cross and dot products.

Use the fact that the dot product between two vectors produces a scalar quantity and that the cross product produces a perpendicular vector.
• Jun 8th 2010, 05:26 AM
Warrenx
Quote:

Originally Posted by Kakariki
Hey!
I am having trouble understanding what this question is answering, and also how to go about answering it! Hopefully some help can be derived from this thread.

Question
Explain where the quantity $\displaystyle \frac{a \bullet b + a \bullet a \times b}{|b|}$ is a vector, scalar, or neither. Explain your answer.

Solution
I don't understand what this question is asking. I know how to tell if something is a scalar or vector quantity (for example the wind blowing at 20km/h is scalar, but the wind blowing at 20km/h going NW is a vector) but I don't know how to apply it to this question!
I also know how to calculate the cross and dot products.