某兴趣小组设计了如图所示的玩具轨道，其中“2008”四个等高数字_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题计算题

某兴趣小组设计了如图所示的玩具轨道，其中“2008”四个等高数字用内壁光滑的薄壁细圆管弯成，固定在竖直平面内（所有数字均由圆或半圆组成，圆半径比细管的内径大得多），底端与水平地面相切。弹射装置将一个小物体（可视为质点）以V_a=5m/s的水平初速度由a点弹出，从b点进入轨道，依次经过“8002”后从p点水平抛出。小物体与地面ab段间的动摩擦因数μ=0.3，不计其它机械能损失。已知ab段长L=1.5m，数字“0”的半径R=0.2m，小物体质量m=0.01kg，g=10m／s²。求：

（1）小物体从p点抛出后的水平射程。

（2）小物体经过数字“0”的最高点时管道对小物体作用力的大小和方向。

答案

解：（1）设小物体运动到p点时的速度大小为v，对小物体由a运动到p过程应用动能定理得

①

小物体自P点做平抛运动，设运动时间为t，水平射程为s，则

②，s=vt ③

联立①②③式，代入数据解得s=0.8m ④

（2）设在数字“0”的最高点时管道对小物体的作用力大小为F，取竖直向下为正方向

⑤

联立①⑤式，代入数据解得F=0.3N ⑥，方向竖直向下

完形填空

A wave of recent research has pointed to the risks of over praising a child. And it seems that how to draw a line between too little praise and too much has become a high-pressure _  _act for parents.
Self-esteem (自尊) serves as a kind of tool to measure how much children feel valued and accepted by     . This sensitivity to others'      develops because of humans' need for social acceptance, which is considered to be      to survival. As early as age 8, children's self-esteem tends to rise and fall in response to feedbacks about      peers see them as likable or attractive.     , it can also be beneficial for kids to feel bad about themselves occasionally, if they behave in selfish, mean or hurtful ways that might      their ability to maintain relationships or hold a job in the future.
In the past, many parents and educators believed that high self-esteem      happiness and success, and kids could gain self-esteem simply by getting      and awards from their parents, teachers and people around. But recently researchers have found self-esteem doesn't _   these desired results. Instead, if parents praise their kids     , their self-esteem becomes focused on being very smart and being the best and being perfect. Building too much self-esteem of the children can not go as planned, making them feel      later on when they hit setbacks (挫折).
According to some experts, it can actually be good for kids to have      self-esteem, at least once in a while. And praise can be      if it disregards the world outside the home. Children who have a      understanding of how they are seen by others tend to get recovered more readily      disappointment, depression or the like. The best path is a      road, helping children develop a positive but      view of themselves in relation to others by praising them for the      they invest and behaviors they are able to sustain, like "It's      that you're working so hard on your homework. "

D．embarrassing

A．settle down

D．bring about

填空题

控件数组的名字由【9】属性指定，而数组中的每个元素由【10】属性指定。