《理论力学》双语教学 第八章 点的合成运动(117P).pptVIP

1 [Example 3] [例3] 曲柄滑块机构 and h;are given. At the moment, find the angular velocity w2 of rod O2E. 已知： h; 图示瞬时 ; 求: 该瞬时 杆的w2 。 See the animation 请看动画 Solution：moving point: point A on O1A; MCS: attached to BCD, SCS: attached to the support. 解：动点:O1A上A点; 动系:固结于BCD上, 静系固结于机架上。 absolute motion: circular motion; 绝对运动：圆周运动; 相对运动：直线运动; relative motion：rectilinear motion; convected motion ：translation;　　　 ，horizontal 牵连运动：平动;　　　 ，水平方向 According to draw the parallelogram of velocities 根据 做出速度平行四边形 Select moving point：point F on BCD MCS：attached to O2E， SCS: attached to the support 再选动点：BCD上F点 动系：固结于O2E上， 静系固结于机架上 ） （ absolute motion: rectilinear motion; 绝对运动：直线运动，　 relative motion：rectilinear motion; 相对运动：直线运动， convected motion ：rotation; 牵连运动：定轴转动， 根据 做出速度平行四边形 According to draw the parallelogram of velocities. The radius of cam C is R，point O and C in the same line at this moment. are known. Find the angular velocity and acceleration of rod OA at this instant. 已知：凸轮半径为R，图示瞬时O、C 在一条铅直线上; 已知; 求: 该瞬时OA杆的角速度和角加速度。 Analysis: Since the contact point between these two rigid bodies varies with time relative to both of them, the contact point is not suitable as a moving point. 分析: 由于接触点在两个物体上的位置均是变化的，因此不宜选接触点为动点。 [Example 4] [例4] 凸轮机构 See the animation 请看动画 absolute motion: rectilinear motion; 绝对运动: 直线运动， relative motion：rectilinear motion; 相对运动: 直线运动， convected motion ：rotation; 　 　 牵连运动: 定轴转动， 方向 direction solution: Take C on the cam as the moving point， and attach MCS to rod OA and SCS to the earth ground. 解: 取凸轮上C点为动点， 动系固结于OA杆上， 静系固结于地面上． ） ( drawing the parallelogram of velocities, we have 做出速度平行四边形,知 According to 根据 According to 根据 做出加速度矢量图 Drawing the vectorial diagram of accelerations, gives 投至? 轴： Projecting them to axis ? , we have: 转向由上式符号决定，0则　　，0 则 Ro