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问题 选择题

如图所示，质量为m的物体，以速度v离开高为H的桌子，当它落到距地面高为h的A点时，在不计空气阻力的情况下，下列判断错误的是（   ）

A．若取地面为零势能面，物体在A点具有的机械能是

B．若取桌面为零势能面，物体在A点具有的机械能是

C．物体在A点具有的动能是

D．物体在A点具有的动能与重力势能的零参考面有关，因此是不确定的

答案

答案：D

运动过程中，小球只受重力作用，机械能是守恒的，所以若取地面为零势能面，物体在A点具有的机械能为。若取桌面为零势能面，物体在A点具有的机械能是

AB正确，重力势能的减小量转化为动能了所以物体在A点具有的动能是，C正确。D错误。

阅读理解

阅读短文，判断下列句子正（T）误（F）。

　　Carol's Cafeteria has the most delicious food in town.  But there is one

problem.  It's not in the busiest part of the town.  It takes about fifteen minutes to

walk there from school. My friends and I usually go to Lenny's Lunch Bar.  It's

closer and the food is really good.

　　The people at Lenny's are also friendlier than those at Carol's. In fact,

Lenny's is the friendliest place in town. They have the biggest hamburgers and the

best salads. But their pizza is pretty bad. You should never have pizza at Lenny's!

( )1. The food at Carol's Cafeteria is good.

(     )2. Lenny's is closer to school than Carol's.

(     )3. Lenny's food is better than Carol's.

(     )4. Lenny's is friendlier than Carol's.

(     )5. Lenny's hamburgers are small.
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选择题

_____Monday morning, we played_______ table tennis.[ ]

A. In;the            

B. On;/

C. At;/              

D. On; the
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