[填空题]
What is the linear speed of a pwj o+;k2ommxgai , gx1)u s0; j4lh5gaois g1d7bm;/o g5usp4 pmnt (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? $m/s$