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问题 多选题

如图所示，木板B放在粗糙的水平面上，木块A放在B的上面，A的右端通过一不可伸长的轻绳固定在直立墙壁上，用力F向左拉动B，使它以速度v做匀速运动，这时绳的张力为T．下面说法正确的是（　　）

A．木板B受到的滑动摩擦力大小等于T

B．T＜F

C．A受到的滑动摩擦力大小等于T

D．若木板B以2v的速度匀速运动，则拉力应为2F

答案

A、木板在抽出过程中相对于地面做匀速直线运动，其上下表面均受滑动摩擦力，而上表面的滑动摩擦力大小等于T，总摩擦力f＞T，故A错误；

B、对木板列水平方向平衡方程得F=f＞T，故T＜F，故B正确；

C、对木块A由平衡条件得，滑动摩擦力大小等于T，故C正确；

D、无论木板以多大的速度匀速运动，都处于平衡状态，而其受到的来自地面和A的滑动摩擦阻力是不变的，因此拉力始终是F，故D错误．

故选BC

选择题

Mary _____ be in London because I saw her in town just now.  

A．mustn’t　　

B．isn’tableto

C．maynot　

D．cannot
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阅读理解
L1PITOR
ABOUT LIPITOR
Lipitor is a prescription medicine．Along with diet and exercise，it lowers “bad” cholesterol(胆固醇)in your blood．It can also raise “good'’ cholesterol.
Lipitor can lower the risk of heart attack in patients with several common risk factors，
including family history of early heart disease，high blood pressure，age and smoking.
WHO IS LIPITOR FOR?
Who can take LIPITOR：
．People who cannot lower their cholesterol enough with diet and exercise
·  Adults and children over l0
Who should NOT take LIPITOR：
．Women who are pregnant，may be pregnant，or may become pregnant. Lipitor may harm your unborn baby.
．women who are breast-feeding．Lipitor can pass into your breast milk and may harm your baby.
·  People with liver(肝脏)problems
 POSSIBLE SIDE EFFECTS OF LIPITOR
Serious side effects in a small number of people：
．Muscle(肌肉)problems that can lead to kidney(肾脏)problems，including kidney failure
．Liver problems．Your doctor may do blood tests to check your liver before you start Lipitor and while you are taking it．
Call your doctor right away if you have：
．Unexplained muscle pain or weakness，especially if you have a fever or feel very fired
．Swelling of the face，lips，tongue，and／or throat that may cause difficulty in breathing or swallowing
·  Stomach pain
Some common side effects of LIPITOR are：
·  Muscle pain
·  Upset stomach
·  Changes in some blood tests
 
 HOW TO TAKE LIPITOR
DO：
．Take Lipitor as prescribed by your doctor.
．Try to eat heart-healthy foods while you take Lipitor.
．Take Lipitor at any time of day, with or without food.
．If you miss a dose(一剂)，take it as soon as you remember.[But if it has been more than
12 hours since your missed dose，wait．Take the next dose at your regular time.
Don’t：
．Do not change or stop your dose before talking to your doctor.
．Do not start new medicines before talking to your doctor.
 
小题1: What is a major function of Lipitor?
A．To help quit smoking.
B．To control blood pressure.
C．To improve unhealthy diet.
D．To lower "bad" cholesterol.
小题2: Taking Lipitor is helpful for              .
A．breast-feeding women
B．women who are pregnant
C．adults having heart disease
D．teenagers with liver problems．
小题3: If it has been over 12 hours since you missed a dose, you should         
A．change the amount of your next doseB．eat more when taking your next dose
C．have a dose as soon as you rememberD．take the next dose at your regular time
小题4: Which of the following is a common side effect of taking Lipitor?
A．Face swelling.B．Upset stomach.
C．Kidney failure. D．Muscle weakness.
小题5: What is the main purpose of the passage?
A．To teach patients ways for quick recovery.
B．To present a report on a scientific research.
C．To show the importance of a good lifestyle.
D．To give information about a kind of medicine.
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