题目

      A major source of teen stress is school exams, and test anxiety is not uncommon. When you recognize your teen is under stress, how can parents help your teen stay calm before an exam?       Be involved. Parents need to be involved in their teen’s work.  36 _ What they look for is your presence — to talk, to cry, or simply to sit with them quietly. Communicate openly with your teen. Encourage your teen to express her worries and fears, but don’t let them focus on those fears.       Help them get organized.  37     Together , you and your teen can work o一光滑圆环固定在竖直平面内，环上套着两个小球A和B（中央有孔），A、B间由细绳连接着，它们处于如图所示位置时恰好都能保持静止状态．此情况下，B球与环中心O处于同一水平面上，B间的细绳呈伸直状态，与水平线成30°夹角．已知B球的质量为m，求细绳对B球的拉力和A球的质量．