题目

Rules on how to be a fit kid Being fit is a way of saying a person; a person eats well, gets a lot of physical exercise, and has a healthy weight. __45．__. If you're a kid who wants to be fit, here are three rules to live by. 1．Eat a variety of foods. You may have a favorite food, but the best choice is to eat a variety. __46．__. Taste new foods and old ones you haven't tried for a while. Some foods, such as green vegetables, are more pleasing the older you get. Shoot for at least five servings of fruits and vegetables a day—two fruits and three vegetables. 2．__47．_ What does一根绳子所能承受的拉力是2.0×104N，能不能用它一次提起10块长2m、宽1m、厚1cm的钢板？（ρ=7.8×103kg/m3）