在一堂前滚翻课上,我给学生提出这样一个问题:“球和木块哪个易于滚动?”接着我拿出了事先准备好的纸球和木块进行演示,并让一个学生出列尝试体验,最后得出结论:球比木块容易滚动。我正陶醉于刚才的情境并准备总结前滚翻的动作要领时,突然,魏宇同学举手提问:“如果作用于木块一 In a pre-rolling class, I asked the student a question: “Which balls and pieces are easy to roll?” Then I took out pre-prepared paper balls and wooden blocks to demonstrate and let a student try out Finally, it is concluded that the ball is easier to roll than wood. When I was reveling in the situation I had just mentioned and prepared to summarize the action points of the previous roll-over, Suddenly, Wei Yu raised his hand and raised his hand to ask: "If it acts on a wooden block,