[填空题]
What is the linear speed of a 7s h :xukmf6wpp9wjw k7d5r-r tl0, 7gpointkfi +;bsl/a 95 y djpt61f/qtv (a) on the equator, $m/s$ (b) on the Arctic Circle (latitude 66.5$^{\circ} $ N), $m/s$ (c) at a latitude of 45.0$^{\circ} $ N, due to the Earth’s rotation? $m/s$