题目

两个质量均为5 kg的铅球，相距1 m时，它们之间的万有引力为多大? 答案：解析：根据万有引力定律F=得F=6.67×10-11×N=1.67×10-9 N.答案：1.67×10-9 NI cleaned the room and did my homework last weekend.I was very ________. A.relaxing　　　　　　 B.tired C.difficult　　　　　　 D.happy