[填空题]
What is the linear speed o;osb+rzcy 0w h)7v fkl7hohe7;;6d em f a p2kha;rze 8hmi3:; tch oint (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? $m/s$