给你一架无砝码、无游码、已调好的等臂天平和一个量杯、细绳、一些细沙及适量的水。（水的密度ρ水已知）。请测出一块小矿石的密度。要求：
（1）写出实验步骤及要测量的物理量。_______________________________
（2）推出用所测物理量表达矿石密度的表达式。表达式：_____________
（1）
①将空量杯放在右盘,在左盘放适量的细砂，使天平平衡；
②在左盘再放上小矿石，在右盘的空量杯中慢慢加水，直至天平再次平衡；
③记录此时量杯中水的体积V1
④取下量杯，在杯中装适量的水，记录此时量杯中水的体积V2
⑤将小矿石放入量杯中，记录此时量杯中水的体积V3。推导：m石=m水=ρ水V1，V石=V3-V2。
（2）ρ石=m石/V石=ρ水V1/（V3-V2）
| 完形填空。阅读下面的短文，选择适当的词。 | |||
| It was Sunday. I never get up early 1__________ Sundays. I sometimes stay in 2__________ until lunchtime. Last Sunday I 3__________ very late. I looked out of the window. It was dark outside. " What a day! " I thought. " It's 4__________ again." Just then, the telephone rang. It 5__________ my aunt Lucy. " I've just arrived 6__________ train," she said, " I'm coming to 7__________ you." " But I'm still having breakfast." I said. " What are you 8__________? " she asked. " I'm having 9__________." I repeated. " Dear me," she said. " 10__________ you always get up so late? It's one o'clock."
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