题目内容
以V0=12m∕s的初速度竖直向上抛出一质量为0.5kg的物体,g取10m/s2。。求:
(1)不考虑空气阻力,小球上升的最大高度和回到抛出点的时间;
(2)如果空气阻力f大小恒为1.0N,求小球回到抛出点时速度大小。
(1)不考虑空气阻力,小球上升的最大高度和回到抛出点的时间;
(2)如果空气阻力f大小恒为1.0N,求小球回到抛出点时速度大小。
(1)2.4s(2)V=4
m/s
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133050973334.png)
:(1)
······1分
=7.2m ······1分
······1分
=2.4s ······1分
(2) 上升过程中, - mgh –fh ="0" -
······2分
整个过程中, -2fh=
-
······2分
解得 V=4
m/s ······2分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133051036679.png)
=7.2m ······1分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133051082596.png)
=2.4s ······1分
(2) 上升过程中, - mgh –fh ="0" -
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133051129658.png)
整个过程中, -2fh=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133051160623.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133051129658.png)
解得 V=4
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133050973334.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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