如图所示,具有初速度的物块,沿倾角为30°、粗糙的斜面向上运动的过程中,受一个恒

题型:选择题

问题:

如图所示,具有初速度的物块,沿倾角为30°、粗糙的斜面向上运动的过程中,受一个恒定的沿斜面向上的拉力F作用,这时物块 加速度的大小为4m/s2,方向沿斜面向下.那么在物块向上运动过程中,正确的说法是

A.物块的机械能一定增加

B.物块的机械能一定减少

C.物块的机械能有可能不变

D.物块的机械能可能增加也可能减少

考点:动能定理
题型:选择题
根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。
Smiling is a great way to make yourself stand out while helping your body to function better. Smile to improve your health, your stress level, and your attractiveness;
      1        
We are drawn to people who smile.There is an attraction factor.We want to know a smiling person and figure out what is so good because anxieties can push people away, but a smile draws them in.
Smiling changes our mood.
Next time you are feeling down, try putting on a smile.      2    Smiling can trick the body into helping you change your mood.
Smiling is appealing.
When someone is smiling they lighten up the room, change the moods of others, and make things happier.A smiling person brings happiness with them.Smile a lot and you will draw people to you.
Smiling relieves stress.
Stress can really show up in our faces.Smiling helps to prevent us from looking tired, worn down, and overwhelmed.     3      The stress should be reduced and you’ll be better able to take action.
Smiling lowers your blood pressure.
When you smile, there is a measurable reduction in your blood pressure.Give it a try if you have a blood pressure monitor at home.Sit for a few minutes and take a reading.Then smile for a minute and take another reading while still smiling.____4____
Smiling lifts the face and makes you look younger.
The muscles we use to smile lift the face, making a person appear younger.Don’t go for a face lift, just try smiling your way through the day—you’ll look younger and feel better.
  5 
Try this test: Smile.Now try to think of something negative without losing the smile.It’s hard.When we smile, our body is sending the rest of us a message that "Life is Good! "
    A.Smiling helps you stay positive.
B.Smiling makes us attractive.
C.Do you notice the difference?
D.Smiling can bring you luck and sorrow.
E.When you are stressed, take time to put on a smile.
F.There’s a good chance that your mood will change for the better.
题型:选择题

客户满意度调查过程的成败首先取决于该调查的( )。

A.实施步骤

B.协同运作

C.数据

D.策划

题型:选择题

We do not permit ________ in the office.

A.others smoking

B.to smoke

C.smoked

D.smoking

题型:选择题

卧式注射成型机的优点是()。

A.机体较矮

B.容易操作加料

C.便于实现自动化操作

D.以上都是

题型:选择题

用电子计算机进行会计核算与手工核算,两者使用的原始会计资料是不一致的。( )

更多题库