题干

国家惠农政策不断出台,农民生活水平不断提高,许多村民为改善居住条件,自建砖混结构的楼房.建房时候所用的长方体实心红砖(红砖规格及参数如下表)的实际承压是必须考虑的一个重要因素.g取10N/kg

红砖规格及参数

0.25m

0.12m

0.05m

红砖的质量

2.25kg

红砖能实际承受的最大压强

1.8×105Pa

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    When we think of food farming we usually think of green fields in the country, outside the city. Sam Chee works on a very different type of farm, in the center of the Canadian city of Toronto. “We grow fruit, vegetables and herbs,” says Sam. “But not many people know the farm is here. You can't see it from the street. We're on top of an office building, 50 meters above the ground.”
    Rooftop farming is becoming popular in cities like Toronto, New York and London. The roofs of buildings are often just wasted space, but this space can be used for growing good fresh food, right in the middle of the city. Sam explains how it works. “We grow everything in big boxes—there are hundreds of them. We catch rainwater to water the plants when the weather is dry.”
    The rooftop farm where Sam works belongs to a restaurant called Green Garden, on the ground floor of the building. The farm produces about half the restaurant's fruit and vegetables. Sam believes that the rooftop farm is what makes Green Garden special. “We help to keep food production local. We don't need to transport this food from anywhere and that saves energy. It's better for the environment.”
    The food from the rooftop is fresher too. “When the fruit and vegetables are ripe we can pick them and use them right away. They taste better when they're really fresh,” says Sam. “I hope that there will be more rooftop farms in the city soon. It could be the farming of the future.”