题目

Nowadays, mobile phones are more and more popular in our society. Even many students of high schools have got their own mobile phone. The mobile phone does offer a lot convenience to us. With a mobile phone, we can call the others not matter where we are. We can also send short messages. But, the mobile phone brings trouble as well. The signals of the phone disturbed our living space too much. Sometimes it will be unsafe or impolite to use a mobile phone. What’s more, it can be bad for the students who pay too more attention to it. It seems it’s not necessary for our middle school 紧急情况逃生时，使用普通破窗锤产生的碎玻璃容易伤人．如图为一种新型破窗锤，使用时将吸盘吸附在窗玻璃上，然后拉长弹性绳，人离玻璃较远后松手，破窗锤在弹力作用下瞬间击碎窗玻璃而不会伤到人．下列有关说法错误的是（ ） A.吸盘能吸附在窗玻璃上是由于受到大气压的作用B.若吸盘面积太小，则拉长弹性绳时容易脱落C.锤头前端做得比较尖是为了增大压力D.松手后，绳的弹性势能主要转化为破窗锤的动能