Question

Vector $\overrightarrow {A} $ has a magnitude of $ 5 $ units, lies in the $ xy $ - plane and points in a direction $ 120^\circ $ from the direction of increasing $ x $ . Vector $\overrightarrow {B} $ has a magnitude of $ 9 $ units and points along the $ z $ -axis. The magnitude of cross product $ \overrightarrow{A} \times \overrightarrow{B} $ is

• A. 30
• B. 35
• C. 40
• D. 45

Answer 1

Answer: (D)

$ |A| = 5, |B | = 9$
Vector $B$ makes angle $90^{\circ}$ from $A$

$A \times B =| A| |B| \,\sin \theta$
$= 5 \times 9 \,\sin\, 90^{\circ}$
$= 45$