装卸工要将质量为50kg的木箱搬到卡车上，找来了长为4.4m的木板，做了一个倾角为37°的斜面．装卸工用大小为500N、方向与斜面成37°的斜向上的拉力F将木箱拉上卡车．已知木箱与木板间动摩擦因数μ=0.5，sin37°=0.6，cos37°=0.8，g=10m/s²．

近年来，我国与机器人相关的企业数量快速增加，但大多数机器人企业规模较小，没有研发能力，企业以组装和代加工为主，主要集中于中低端产产品，核心零件依赖进口，同质化竞争加剧，并已出现“高端产业低端化”的趋势。中国机器人产业的健康发展需要（  ）

①坚持创新发展的原则，增强自主研发能力

②减少政府干预，发挥市场决定资源配置的作用

③政府制定科学规划，支持和引导发展方式的转变

④提高准入门槛，限制民间资本机器人产业

    When I was growing up, I didn't remember hearing the words “I love you” from my father. When your father1 says these words to you when you are a (n)2it gets tougher and tougher for him to say these words as he gets 3To tell the truth, I could not honestly remember 4 I had last said those words to him either. I decided to 5my ego (自尊心) aside and make the first move. After 6in our next phone conversation I blurted out (突然说出) the words, “Dad... I love you!”

    There was a 7at the other end and he awkwardly (笨拙地) replied, “Well, same back to you!”

    I smiled and said, “Dad, I know you 8 me, and when you are ready, I know you9 say what you want, to say.”

    Fifteen minutes later my 10 called and nervously asked, “Paul11 is okay?” I explained to her perfectly.

    A weeks later, Dad 12 our phone conversation with the words, “Paul, I love you.” I was at work during this13and the tears were rolling down my cheeks as I finally “14” the love. As I sat there in tears, I 15 that this special moment had taken our father-son 16 to a new level.

    A short while after this 17 moment, my father narrowly18 death following heart operation. I have often thought 19 I did not take the first step and Dad did not 20 the operation, I would have never “heard” the love.