A girl runs around a circular track of radius R with a constant speed v. At the moment the girl has run half of the track, the magnitude of her average velocity is
A) $\mathcal { V }$
B) $0$
C) 2v/. $\pi$
D) $2 v$
E) 2v. $\pi$

Question

Quizplus · Accepted Answer

The average velocity of an object is defined as the displacement divided by the time taken. In this case, after running half the track, the girl's displacement is the diameter of the circular track (2R), and the time taken is the half-circumference of the track divided by her speed (πR/v). Therefore, the magnitude of her average velocity is $2R / (\pi R / v) = 2v / \pi$.

A Girl Runs Around a Circular Track of Radius R V\mathcal { V }V

A Girl Runs Around a Circular Track of Radius R $\mathcal { V }$