Question

\(\vec j\times\vec i=\) ?

• A. \(\vec k\)
• B. \(-\vec k\)
• C. \(\vec 0\)
• D. \(1\)

Hint:

Cross product is anti-commutative: \(\mathbf{a}\times\mathbf{b}=-(\mathbf{b}\times\mathbf{a})\).

Answer 1

The Correct Option is B

Right–hand rule: \(\vec i\times\vec j=\vec k\). Swapping the order changes the sign: \[ \vec j\times\vec i=-(\vec i\times\vec j)=-\vec k. \]