题目

假如你是李华，你的学校要举行运动会，组委会现征集志愿者，请给学校组委会负责人王先生写一封信，申请成为一名志愿者。要点如下：1）个人情况；2）为什么申请当志愿者；3）你将如何当好这个志愿者。注意：词数100左右。 答案：Dear Mr. Wang, My name is Li Hua, a student in Grade one. Knowing that the sports meeting will be held on our campus, I can't wait to write to you to apply to be a volunteer. As a sports lover, I have a general idea of the rules of different events. In addition, I am also good at communicating with others and eager to lend a hand to people in need. With the spirit of voluntary work rooted in my h质量为50kg的某人沿一竖直悬绳匀速向上爬，在爬高3m的过程中，手与绳子之间均无相对滑动，重力加速度g取10m/s2，则下列说法正确的是（ ）A．绳子对人的静摩擦力做功等于人的重力势能的增加B．绳子对人的静摩擦力做功等于人的机械能的增加C．绳子对人的静摩擦力不做功D．人克服自身重力做功使其重力势能增加1500 J