题干

阅读小资料:生活中的小窍门无处不在.例如,锤子的锤头变松了,可以用撞击锤柄下端的方法,使锤头紧套在锤柄上(如图所示),反复几次会套得更牢.

阅读上述小资料,请你在小组合作学习交流中,给小组其他同学解释“使锤头紧套在锤柄上”所包含的物理道理.

上一题 下一题 0.0难度 选择题 更新时间:2012-12-27 02:06:19

答案(点此获取答案解析)

答:因为锤头与柄原来都向下运动,锤柄撞在板凳上时受到阻力作用,改变了它的运动状态,由运动变为静止,而锤头由于惯性,仍保持原来运动状态,继续向下运动,这样反复几次,锤头就紧套在锤柄上了.

同类题5

七选五

    Nail-biting(咬指甲) is one of the most common annoying habits in children. ____ But you needn't worry too much and as soon as you realize what's causing nail-biting, you can help your child overcome and stop it. So, here's what you can do about it.

    ____In some cases, children won't even realize they are biting their nails, let alone know why they are doing it. So make sure you have a conversation with your child (if he/she is old enough) and make him/her realize he/she is doing it and try to figure out why it's happening.____ It's important to agree on the level of your involvement. If he/she wants help, create a secret reminder that will make him/her stop without embarrassing him/her.

    Give alternatives (替代物).____ Depending on the age of the child, there are several things that you can offer such as a small ball, Play-Doh games, or any kind of other small toys.

    Use bitter solutions(溶液). Forcing a child to keep this solution on his/her fingers may feel like a punishment.____ Everything else will only lead to embarrassment and discouragement. Furthermore, some of these solutions contain pepper which burns if it enters a child's mouth or eyes. But if you have an adolescent child who wants to quit biting his/her nails, you may suggest and try out this solution.

A.It's also likely to continue as the child grows up.

B.Help the child become aware of the habit.

C.You should also consider asking for professional help.

D.Make an agreement on how you're going to stop it together.

E.The best thing children can do is communicate with their parents.

F.The child needs to go through the process painlessly and in agreement with you.

G.That will keep his/her hands occupied when he/she is likely to bite his/her nails.