问题 选择题

在光滑水平面上有一个内外壁都光滑的质量为M的气缸,气缸内有一质量为m的活塞,已知M>m,活塞密封一部分理想气体。现对气缸施加一个水平向左的拉力F(如图甲所示)时,气缸的加速度为a1,封闭气体的压强为p1,体积为V1;若用同样大小的力F水平向左推活塞(如图乙所示),此时气缸的加速度为a2,封闭气体的压强为p2,体积为V2。设密封气体的质量和温度均不变,则____(填选项前的字母)

  

A.a1 = a2,p1<p2,V1 < V2

B.a1 = a2,p1<p2,V1 > V2

C.a1 < a2,p1>p2,V1 < V2

D.a1 > a2,p1>p2,V1 > V2

答案

答案:B

把活塞和气缸看做一个整体,由牛顿第二定律可知a1 = a2,以活塞为研究对象,内部气体压强会增大,内部气体体积会减小,B对;

单项选择题 B型题
阅读理解

Halloween Fun Run

Start date: Sept. 9---Oct. 28

Rate: $80 / $10 per class

Time: 4:15---5:15

Dress according to weather. Please note that your child does not need to run races in order to participate in this run training. Focus is on fun and participation. No run experience needed. All ages of kids are welcome.

Class format: 40 minutes of running and running games.

Saturday Indoor Long Rides 2---5 pm

Start date: Sat. Oct.17---Dec.19

Pre-registered rate: $200 / $ 20 per ride

Drop-in rate: $22

This class is designed for road riders, Ride to Conquer Cancer participants, athletic cross-training, and people wanting a great weekly challenge. Participants are encouraged to work within their own level of comfort. No previous riding experience needed; all are welcome. We will begin long rides at 2 hours, and after a few weeks add 15 minutes until we reach 3 hours. At that point, rides will remain 3 hours in length until the outdoor season begins.

Please bring liquid that you drink, nutrition and a towel. Room accommodates 18 spin bikes(健身车).

Family Fun Fit Private Coaching

Learn with Christina Kaufmann. Family Fun Fit’s Private Coaching Service begins with a one-hour face-to-face meeting where we map out where you are and where you wish to be. Next, Christina creates a personalized training program and schedule that will systematically train you and encourage you to achieve your desired goal.

Clients(顾客) have the access to the coach via email or phone. Christina’s past clients have successfully achieved their goals.

This service is ongoing(进行中). Cost is $150 per month.

小题1:Halloween Fun Run is held to make kids ______.

A.learn how to compete

B.become professional runners

C.have a good time

D.build self-confidence小题2:When you attend Saturday Indoor Long Rides, you’re required to _____.

A.begin long rides at three hours

B.have precious riding experience

C.prepare some drinks

D.be a road rider小题3:What do we know about Christina Kaufmann ?

A.Her class is very lively and interesting.

B.She gives her instructions on the phone in most cases.

C.She offers service for free.

D.She helps make training plans.小题4:What’s the purpose of the text ?

A.To introduce Christina Kaufmann.

B.To help people form good habits.

C.To try to teach people how to keep fit.

D.To encourage people to join the club.