题干

水平面上甲、乙两物体,在某时刻动能相同,它们仅在摩擦力作用下停下来,如图所示的a、b分别表示甲、乙两物体的动能E和位移s的图象,则(      )

①若甲、乙两物体与水平面动摩擦因数相同,则甲的质量较大
②若甲、乙两物体与水平面动摩擦因数相同,则乙的质量较大
③若甲、乙质量相同,则甲与地面间的动摩擦因数较大
④若甲、乙质量相同,则乙与地面间的动摩擦因数较大            
以上说法正确的是(     )

A:①③

B:②③

C:①④

D:②④

上一题 下一题 0.0难度 选择题 更新时间:2019-04-03 09:43:31

答案(点此获取答案解析)

A

同类题1

阅读理解

    People can't see you when you're speaking on the phone,but they can hear you.So,the way you speak is especially important.In fact,researchers have calculated that 80% of communication over the phone is through your tone of voice; and only 20% is from the words you use.Here are our top tips on how to speak over the phone.

⒈Facial Expressions

    Your facial expression can influence your voice.For example,if you smile,your voice will sound warm and friendly,just the opposite,if you have an angry look on your face,it can make you sound unpleasant.

⒉Volume

    If you speak too loudly,you could sound angry.And if you speak too softly,it'll be difficult to hear you.So,speak loudly enough to be heard clearly,but not so loud that you're shouting.

⒊Pace

    The pace of your voice is how quickly you speak.And this can show how you feel.For example,an angry person might speak faster than normal.Or a downhearted person might speak very slowly.Try speaking a little more slowly than normal.This will make you sound confident,and it'll make it easier for the other person to understand you.

⒋Gestures

    Gesturing can influence the tone of your voice.When you gesture,you bring more air into the lungs,which can make your voice sound warmer.Gestures are also useful to help you stress the right words or even find the words you need.The best thing about gesturing during a phone call is that no one can see what you're doing,so you can gesture as wildly as you like!

⒌Movement

    If you're feeling nervous,stand up and move around.It will reduce the nervousness in your body and help your voice to sound more confident.

⒍Pauses (停顿)

    Using pauses every now and then can help you to slow down.This will make you sound more confident and in control.Also,if you pause after giving some new information,it'll give the other person time to understand it.At the same time,listen to how the other person uses pauses.They could tell you something about the speaker's feeling.For example,when a speaker is really angry,he might use pauses and says,"I…am…so…angry…"