The second’s hand of a clock is 2.0 cm long. The average speed and modulus of average velocity of the tip of the seconds hand in 15 s are                                 

Given that the tip of seconds hand started at A and reached B in 15s

r = 2.0s

Distance $=\frac{2\pi r}{4}=\frac{\pi r}{2}$

Displacement = AB

From $\Delta \text{OAB}$

${\text{AB}}^{\text{2}}={\text{OA}}^{\text{2}}+{\text{OB}}^{\text{2}}$

${\text{AC}}^{\text{2}}=2^2+2^2$

${\text{AC}}^{\text{2}}=4+4=8$

$\text{AC}=\text{2}\sqrt{2}$

Average speed $\text{v}=\frac{\text{s}}{\text{t}}=\frac{\pi }{15}{\text{cms}}^{-1}$

Average velocity $\overrightarrow{v}=\frac{\text{s}}{\text{t}}=\frac{2\sqrt{2}}{15}{\text{cms}}^{-1}$