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一、提出问题如图1,用双手挤压四块砖 A、B、C、D 向上提起停在空中,砖块 A 与 B、B 与 C、C与 D 之间都存在静摩擦吗?二、问题答案因 A 与 B、C 与 D 之间有相对运动的趋势,故 A 与 B、C 与 D 之间有静摩擦;而 B与 C 分别对于 A 与 D 具有相同的相对运动趋势方向
First, raise the question as shown in Figure 1. Use two hands to squeeze the four bricks A, B, C, and D to lift up and stop in the air. Is there any static friction between the bricks A and B, B and C, C, and D? The answer to the question is due to the tendency of relative movement between A and B, C and D, so there is static friction between A and B, C and D; and B and C have the same relative movement trend direction for A and D respectively.