Question

A vector of magnitude a is rotated through an angle q. What is the magnitude of the change in the vector ?

• A. 2a sin $\frac{\theta}{2}$
• B. 2a cos$\frac{\theta}{2}$
• C. 2a sin q
• D. 2a cosq

Answer 1

Answer: (A)

2a sin $\frac{\theta}{2}$

Answer 2

$\left| \overset{\rightarrow}{\Delta r} \right|$= $\left| {\overset{\rightarrow}{r}}_{f} - {\overset{\rightarrow}{r}}_{i} \right|$ = 2 a sin (q/2) [Q r_f = r_i = a]