说明：  海面上一轮船沿直线匀速前行，速度为30公里/小时，船上有一雷达可用来测距、测角，船长关心的是周围目标那些是活动的船，那些是不动的岩石，若是活动的船，请按下面假设，分析有关因素，给出船的运动方向和速度。
(ships on the sea along a straight uniform before the trip and a speed of 30 km/hour, On board there is a radar can be used to measure the distance and angle measurement, the captain of concern is around the goal of those activities is the boat. those are immobile rocks, if the ship by the following assumptions, analysis of the relevant factors, the boat is the direction and speed of movement.)