题目内容
质量为m的物体以速度v0竖直向上抛出,物体落回地面时,速度大小为
,设物体在运动中所受空气阻力大小不变.
(1)求物体运动过程中所受空气阻力的大小;
(2)若物体落地碰撞过程中无能量损失,求物体运动的总路程.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453417371.gif)
(1)求物体运动过程中所受空气阻力的大小;
(2)若物体落地碰撞过程中无能量损失,求物体运动的总路程.
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453448475.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453433436.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453448475.gif)
(1)设物体所受阻力为f,由动能定理知:
上升过程:-(mg+f)h=0-![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453464441.gif)
下降过程:(mg-f)h=
-0
两式相比得:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453479679.gif)
故f=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453433436.gif)
(2)设物体从抛出到停止时运动的总路程为l,对全程由动能定理知:WG+Wf=Ek2-Ek1,
0-fl=0-
,
所以l=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453526521.gif)
上升过程:-(mg+f)h=0-
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453464441.gif)
下降过程:(mg-f)h=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453464509.gif)
两式相比得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453479679.gif)
故f=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453433436.gif)
(2)设物体从抛出到停止时运动的总路程为l,对全程由动能定理知:WG+Wf=Ek2-Ek1,
0-fl=0-
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453464441.gif)
所以l=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120453526521.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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