创新是一个民族的____，是一个国家兴旺发达的____。

    It's very important(重要的) for us to be healthy. Now I'll tell you how I can be healthy. I often eat fruit and vegetables. I don't like to eat hamburgers. They are not good for my health. I have a balanced diet. Many foods are important, such as rice, meat, eggs, vegetables and fruit. I like to eat apples. As the saying(谚语) says, “An apple a day keeps the doctor away.” And I also like doing sports. I like running in the morning. I play basketball in the afternoon with my friends. And sometimes I play ping­pong with my family at the gym on Saturdays. I think I'm healthy and strong. What about you?

健身用的拉力器结构如图所示，在拉杆处用力往下拉，能把配重提起从而起到锻炼身体的作用．

（1）图中A是一个 ____滑轮．

（2）已知配重的重力为500牛，不计摩擦和绳重，当将配重匀速拉起时，作用在拉杆上的力 ____500牛（填“大于”“等于”或“小于”）．

（3）当重物被提升1米时，拉力对重物所做的功是　 ____　焦．

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