Question

question 9
the second hand on a watch has a length of 4.50 mm (millimeter) and makes one revolution in 60.00 s. what is the speed of the end of the second hand as it moves in uniform circular motion? hint: convert length from millimeter to meter, see metric prefixes from chapter 1.
2.36×10⁻⁵ m/s
2.67×10⁻³ m/s
9.42×10⁻⁴ m/s
5.34×10⁻³ m/s
4.71×10⁻⁴ m/s

Explanation:

Step1: Convert length to meters

$r = 4.50\ mm=4.50\times10^{- 3}\ m$

Step2: Calculate the circumference

The formula for the circumference of a circle is $C = 2\pi r$. So $C=2\pi\times(4.50\times 10^{-3}\ m)$

Step3: Calculate the speed

Speed $v=\frac{d}{t}$, and in one - revolution, $d = C$. Given $t = 60.00\ s$. So $v=\frac{2\pi\times4.50\times 10^{-3}\ m}{60.00\ s}\approx4.71\times 10^{-4}\ m/s$

Answer:

$4.71\times 10^{-4}\ m/s$