论文部分内容阅读
在学习压强知识前,应使学生先建立起正确的压力概念。物体因受重力作用,便对支持面有向下的压力,有的学生常由此错误地引伸为“压力的大小等于重力”,甚至认为“压力就是重力”。为了纠正上述错误认识,教师可制作如下图所示的复合投影片,边投影边和学生讨论分析。先投影出水平桌面上的墨水瓶,压在竖直墙壁上的木块和停在斜坡上的汽车,再用复片投影出它们各自受到的重力G,通过分析讨论最后用复片投影出它们各自对水平桌面、竖直墙壁和斜坡的压力F,这样教学,能开阔学生的思路,能使学生直观地认识到压力是垂直作用在物体表面上的力,而重力是物体由于地球吸引而受到的力,它们的大小不一定相等,方向也不一定相同,更不是属于同一种性质的力。
Before studying pressure knowledge, students should first establish the correct concept of stress. Because of gravity, the object has downward pressure on the support surface. Some students often mistakenly extend this as “the size of the pressure is equal to the gravity,” and even think that “pressure is the gravity.” In order to correct the above misunderstandings, the teacher can make a composite slide as shown in the figure below, and discuss the analysis with the students at the edge of the projection. First project the ink bottles on the horizontal table, press the blocks on the vertical wall and the cars parked on the slope, and then use the multiplex to project their respective gravitational force G. After analyzing the discussion, project them out using the multiplex. With their respective pressures on the horizontal table, vertical walls and slopes, such teaching can broaden the students’ thinking and enable students to intuitively recognize that pressure is the force acting perpendicular to the surface of the object, and that gravity is the object’s attraction to the earth. Their forces are not necessarily the same size, their directions are not necessarily the same, and they are not forces of the same nature.