题目

(2017·全国卷Ⅰ)This trend, ________ was started by the medical community (医学界) as a method of fighting heart disease, has had some unintended side effects such as overweight and heart disease. 答案：which 先行词为this trend，且非限制性定语从句中缺少主语，故用which引导该定语从句。（1）如图所示，工人用F=200 N沿斜面向上的推力，将重力为300N的木箱推上斜面．请作出木箱受到的重力和推力的示意图．（2）小强用力踢足球，踢出后的足球在水平地面上越滚越慢，请在图中画出足球滚动中受到力的示意图．