一块写有校训的花岗岩石料质量为31.8t、密度为2.65×103kg/m3，立在用砖砌成的长4m、宽2m、高0.5m的水平基座上，石料与基座的接触面积为2.12m2。已知砖的密度为2.05×103kg/m3，基座砖缝中水泥砂浆的密度与砖的密度相同。(g取10N/kg)
求：
石料对基座与基座对地面的压强之比。
参考答案：基座受到的重力大小：
G基=m基g=ρ基V基g=2.05×103kg/m3×(4m×2m×0.5m)×10N/kg=8.2×104N
基座对地面的压强：
p基=F/S基=(G石+G基)/S基=(3.18×105N+8.2×104N)/(4m×2m)=5×104Pa
石料对基座和基座对地面的压强之比p石:p基=3:1
| 完形填空 I finished my last work of the week and could hardly wait to get home, take off my nursing shoes, and relax. As I _1_ my car, I saw one of my _2_ standing by the bus stop. I thought it would only take a couple of extra minutes to give her a ride home, and _3_, it was too cold to be standing outside on the coldest _4_ in January. I didn't know where she lived, but I was _5_ I would be able to find my way back. We _6_ about our work as I drove and _7_ we knew it, we arrived at her house. I started driving back. _8_ looked familiar, but at first that didn't _9_ me. But soon I _10_ something wrong. I recognized nothing. But I told myself to stay _11_. I was _12_ neighborhoods, streets and even streetlights. I no longer knew where I was now. How could I be so stupid! I looked down at my _13_. It was now 2:30 a.m. My gas was slowly running out. I _14_ the car and turned off the engine. In total defeat, I put my head down on the wheel, _15_. Then I raised my head and saw a(n) _16_ down the road in front of me. I turned my headlights on. A car! I drove a little _17_, got out of my car and knocked on the window of that car. An elderly man _18_ rolled his window down. I said that I didn't know how to get back into town. In silence, he started driving. I ran back to my car and drove behind him. Finally I _19_ a familiar street. As I turned to head home, the car disappeared. Then I _20_ my driveway (车道) when the warning light for my gas tank (汽油箱) turned on. Though so many years have passed, I still thank the old man from my deepest heart. | ||||
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