Hướng dẫn
- Đối với kim giờ:
$\begin{array}{l} {T_h} = 12.60.60 = 43200s\\ \Rightarrow {\omega _h} = \frac{{2.\pi }}{{{T_h}}} = 1,{45.10^{ - 4}}rad/s\\ \Rightarrow {v_h} = r.\omega = 2,{5.10^{ - 2}}.1,{45.10^{ - 4}} = 3,{4.10^{ - 6}}m/s \end{array}$
- Đối với kim phút:
$\begin{array}{l} {T_{ph}} = 60.60 = 3600s\\ \Rightarrow {\omega _{ph}} = \frac{{2.\pi }}{{{T_{ph}}}} = 1,{74.10^{ - 3}}rad/s\\ \Rightarrow {v_{ph}} = r.\omega = {3.10^{ - 2}}.1,{45.10^4} = 5,{2.10^{ - 5}}m/s \end{array}$
$\Rightarrow \frac{{{\omega }_{h}}}{{{\omega }_{ph}}}=\frac{1,{{45.10}^{-4}}}{1,{{74.10}^{-3}}}\Rightarrow {{\omega }_{ph}}=12{{\omega }_{h}}$
$\Rightarrow \frac{{{v}_{h}}}{{{v}_{ph}}}=\frac{3,{{4.10}^{-6}}}{5,{{2.10}^{-5}}}\Rightarrow {{v}_{ph}}=14,4{{v}_{h}}$
