题目

    An eight-year-old boy named Liangliang liked watching cartoons every day instead of doing his homework, so his mother stopped him from watching cartoons. Liangliang called the police to take his mother away—such a “good reason” to call the police.    Most people would just laugh it off. However, it shows that something is wrong with our education. It rings alarm to our Chinese parents to think about it.    Parents should ask themselves why they’re so angry when their kids want to watch cartoons instead of doing homework. Kids are supposed to be simple and naughty(顽皮). 地球半径为R，地球表面的重力加速度为g，若高空中某处的重力加速度为g/2，则该处距地球表面的高度为____________，在该高度绕地球做匀速圆周运动的卫星的线速度大小为______________。