问题 填空题

“研究合力与分力的关系”的实验情况如图甲所示,其中A为橡皮条的固定点,用两个弹簧秤同时拉橡皮条,把结点拉到O位置,再用一个弹簧秤将橡皮条的结点再次拉到O位置,图乙是在白纸上根据实验结果画出的图.

(1)图乙中的F与F′两力中,方向一定沿AO方向的是______.

(2)本实验采用的科学方法是______

A.理想实验法 B.等效替代法 C.控制变量法 D.建立物理模型

(3)其中正确的是______(填入相应的字母)

A.两根细绳必须等长

B.橡皮条应与两绳夹角的平分线在同一直线上

C.在使用弹簧秤时要注意使弹簧秤与,木板平面平行.

答案

F是通过作图的方法得到合力的理论值,而F′是通过一个弹簧称沿AO方向拉橡皮条,使橡皮条伸长到O点,使得一个弹簧称的拉力与两个弹簧称的拉力效果相同,测量出的合力.故方向一定沿AO方向的是F′,由于误差的存在F和F′方向并不在重合.

(2)实验中两次要求效果相同,故实验采用了等效替代的方法,故ACD错误,B正确.

故选:B.

(3)A、本实验中我们只需使两个力的效果与一个力的效果相同即可,细绳的长度是否相等与本实验无关.故A错误;

B、本实验中我们只需使两个力的效果与一个力的效果相同即可,合力不需要一定过两分力的角平分线,且两分力也不一定相等,故B错误;

C、本实验是通过在白纸上作力的图示来验证平行四边定则,为了减小实验误差,弹簧秤、细绳、橡皮条都应与木板平行,故C正确;

故选:C.

故答案为:(1)F′.

(2)B

(3)C

填空题
阅读理解

Some people think that success is only for those with talent or those who grow up in the right family,and others believe that success mostly comes down to luck.I'm not going to say luck,talent,and circumstances don't come into play because they do.Some people are born into the right family while others are born with great intelligence,and that's just the reality of how life is.

However,to succeed in life,one first needs to set a goal and then gradually make it more practical.And,in addition to that,in order to get really good at something,one needs to spend at least 10,000 hours studying and practising.To become great at certain things,it'll require even more time,time that most people won't put in.

However,to succeed in life,one first needs to set a goal and then gradually make it more practical.And,in addition to that,in order to get really good at something,one needs to spend at least 10,000 hours studying and practising.To become great at certain things,it'll require even more time,time that most people won't put in.

This is a big reason why many successful people advise you to do something you love. If you don't enjoy what you do,it is going to feel like unbearable pain and will likely make you quit well before you ever become good at it.

This is a big reason why many successful people advise you to do something you love. If you don't enjoy what you do,it is going to feel like unbearable pain and will likely make you quit well before you ever become good at it.

When you see people exhibiting some great skills or having achieved great success,you know that they have put in a huge part of their life to get there at a huge cost.It's sometimes easy to think they got lucky or they were born with some rare talent,but thinking that way does you no good,and there's a huge chance that you're wrong anyway.

Whatever you do,if you want to become great at it, you need to work day in and day out,almost to the point of addiction,and over a long period of time.If you're not willing to put in the time and work,don't expect to receive any rewards.Consistent, hard work won't guarantee you the level of success you may want, but it will guarantee that you will become really good at whatever it is you put all that work into.

小题1:Paragraph 1 mainly talks about ________.

A.the reasons for success

B.the meaning of success

C.the standards of success

D.the importance of success小题2:Successful people suggest doing what one loves because ________.

A.work makes one feel pain

B.one tends to enjoy his work

C.one gives up his work easily

D.it takes a lot of time to succeed小题3:What can we infer from Paragraph 4?

A.Successful people like to show their great skills.

B.People sometimes succeed without luck or talent.

C.People need to achieve success at the cost of life.

D.It helps to think that luck or talent leads to success.小题4:What is the main theme of the passage?

A.Having a goal is vital to success.

B.Being good is different from being great.

C.One cannot succeed without time and practice.

D.Luck,talent and family help to achieve success.