杠杆该如何使用？生活中又有哪些应用？
当支点到动力点的距离大于支点到阻力点的距离时，省力。当支点到动力点的距离小于支点到阻力点的距离时，费力。当支点到动力点的距离等于支点到阻力点的距离时，不省力也不费力。跷跷板、夹子等。
汉武帝是中国历史上具有雄才大略的皇帝，下列属于他为巩固大一统而采取的措施是（ ）
①开创皇帝制度 ②实行“推恩令”，允许诸侯王将自己的封地分给子弟 ③实行休养生息政策 ④“罢黜百家，独尊儒术”
每周一学校都要举行庄严的升国旗仪式，让我们体会到了国旗的神圣。某同学产生了用所学知识测量旗杆高度的想法。在地面距杆脚5米的地方，他利用测倾器测得杆顶的仰角为α，且tanα=3,则杆高（不计测倾器的高度）为（ ）
A
Linda，14
My mother does most of the housework like cooking and folding the clothes.My father can only do the washing，sweep the floor and take out the rubbish.He really needs to learn how to do the housework.
Celina，13
My mother and my father do 50% of the housework each.My mother does the washing and cleans the living room.My father makes the bed and drives me to school.
Paul，16
My father doesn't do a lot but he tries to help.He hangs__up the clothes after my mother washes them and my mother is happy that he always gives her a hand.
Bill，15
My mother is a doctor.She is busy with her work every day，so she has little time to do the housework.In fact，she isn't good at doing it.So my father has to do most of it.Sometimes my grandmother comes to help.
