如图所示，两个质量均为M的星体，O为两星体连线中点，PQ是其连线的垂直平分线，一个质量为m的物体从O沿OP方向一直运动下去，则它受到的万有引力大小变化情况是（ ）
A．一直增大
B．一直减小
C．先增大，后减小
D．先减小，后增大
因为在连线的中点时所受万有引力的和为零，当运动到很远很远时合力也为零（因为距离无穷大万有引力为零）而在其他位置不是零所以先增大后减小．
故选C．
In my dream, the weather 67 fine and I came to a nice beach. There were few people on the beach and I 68 to swim in the sea. While I was swimming, some 69 fish followed me all the time. When I stopped, they came to swam 70 me. Then, one of the fish began to talk with me. It 71 Chinese, too! We had a wonderful conversation. Soon we became good 72 and it invited me to visit the place where they lived. 73 I heard a voice, “Weiwei, it’s time to get up! Breakfast is ready!” It was Mom’s voice. Just then I woke up from my sweet dream 74 had to face the real world again. My dream was 75 like a cartoon film, wasn’t it? |