Answer
The linear speed of the tip is $~~(\frac{14~\pi}{15})~mm/s~~$ which is $~~2.93~mm/s$
Work Step by Step
The second hand of a clock moves through an angle of $2\pi$ radians in a time of 60 seconds. We can find the angular speed:
$\omega = \frac{\theta}{t}$
$\omega = \frac{2\pi~rad}{60~s}$
$\omega = \frac{\pi}{30}~rad/s$
We can find the linear speed of the tip:
$v = \omega~r$
$v = (\frac{\pi}{30}~rad/s)(28~mm)$
$v = (\frac{28~\pi}{30})~mm/s$
$v = (\frac{14~\pi}{15})~mm/s = 2.93~mm/s$
The linear speed of the tip is $~~(\frac{14~\pi}{15})~mm/s~~$ which is $~~2.93~mm/s$