根据上传图片题目，生成运动过程视频---**Question:**
4. (2023·内蒙古兴安盟·统考中考真题) 如图所示, 工人用滑轮组将重为200N的货物10s内匀速提升6m, 拉力为150N。忽略绳重及摩擦, 下列说法正确的是 ( )
**Diagram Description:**
* **Type:** Pulley system diagram.
* **Main Elements:**
* Three pulleys are shown. Two fixed pulleys are mounted on an upper support structure. One movable pulley is attached below the fixed pulleys.
* A rope is threaded through the pulleys. One end of the rope is attached to the upper support near one of the fixed pulleys. It goes down around the movable pulley, then up and around the two fixed pulleys. The other end is being pulled downwards by a person.
* A grey rectangular object (labeled as goods) is attached to the movable pulley.
* A person is depicted pulling the free end of the rope downwards.
* There is a horizontal surface below, indicated by hatching.
**Options:**
A. 绳子自由端移动的速度是 1.8m/s
B. 该滑轮组的机械效率为 80%
C. 拉力做功的功率是 90W
D. 该滑轮组的动滑轮重为 100N
视频信息
答案文本
视频字幕
Let's analyze this pulley system problem step by step. We have a worker using a pulley system with two fixed pulleys and one movable pulley to lift a 200 Newton load 6 meters in 10 seconds, using a pulling force of 150 Newtons.
To solve this problem, we first need to identify how many rope segments support the movable pulley. Looking at the diagram, we can see that there are 2 rope segments supporting the load. This is our mechanical advantage factor, n equals 2.
Now let's evaluate the options. For option A, when the load moves up 6 meters, the rope end moves 12 meters because n equals 2. The rope speed is 12 meters divided by 10 seconds, which equals 1.2 meters per second, not 1.8. For option B, the mechanical efficiency is useful work over total work, which is 1200 joules over 1800 joules, equals 66.7 percent, not 80 percent.
For option C, the power equals total work divided by time, which is 1800 joules divided by 10 seconds, equals 180 watts, not 90 watts. For option D, using the pulley formula, the pulling force equals the sum of load weight and movable pulley weight divided by n. Solving for the movable pulley weight: 100 Newtons. Option D is correct, so the answer is D.
Let's summarize our analysis. Option A gives an incorrect rope speed of 1.8 meters per second when the actual value is 1.2. Option B gives an incorrect efficiency of 80 percent when the actual value is 66.7 percent. Option C gives an incorrect power of 90 watts when the actual value is 180 watts. Only option D is correct, stating that the movable pulley weighs 100 Newtons, which matches our calculation using the pulley system formula. Therefore, the correct answer is D.