Question

如圖所示，已知傾角為θ=45°、高為h的斜面固定在水平地面上．一小球從高為H（h<H<h）處自由下落，與斜面做無能量損失的碰撞后水平拋出．小球自由下落的落點(diǎn)距斜面左側(cè)的水平距離x滿足一定條件時，小球能直接落到水平地面上．

    （1）求小球落到地面上的速度大��；

    （2）求要使小球做平拋運(yùn)動后能直接落到水平地面上，x應(yīng)滿足的條件；

    （3）在滿足（2）的條件下，求小球運(yùn)動的最長時間．

Answer 1

（1）P=I²R                                                                            2分

I=1A                                                                                                                                                   1分

方向M到P                                          2分

（2）Fv=I²（R+r）                                                                       2分

_{v=10m/s                                                             2分}

 

或者：

F=BIL                                               1分        

BL=0.5Tm                                         1分

BLv=I（R+r）                                          1分

v=10m/s                                             1分         

（3）,                                                                                                                   _1分       

                                                            1分

                                                                     2分

a=0.5m/s²                                                                     1分

方向向左                                                  1分