）人站在h高处的平台上，水平抛出一个质量为m的物体，物体落地时_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

）人站在h高处的平台上，水平抛出一个质量为m的物体，物体落地时的速度为v，以地面为重力势能的零点，不计空气阻力，则有

A．人对小球做的功是

B．人对小球做的功是

C．小球落地时的机械能是

D．小球落地时的机械能是

答案

AD

人对小球做功等于小球动能增量，B错；小球从抛出到落地由动能定理A对；小球落地时重力势能为零，只有动能，所以机械能为，D对；C错；

补全对话，情景问答

读问句，选择正确的答句。

(     ) 1. What are you going to do tomorrow afternoon?
(     ) 2. How does your father go to Nanjing?
(     ) 3. When did Lily go to visit the Great Wall?

(     ) 4. Where does his brother have piano lessons?
(     ) 5. Which girl is her little sister?

A. He has piano lessons at Miss Lee's home.
B. I'm going to see a new film tomorrow afternoon.
C. The girl in a pink dress is her little sister. She is
very pretty.
D. She went to visit the Great Wall last holiday.
E. He goes to Nanjing by train.

选择题

下列实验基本操作错误的是

A．点燃酒精灯

B．检查装置气密性

C．滴加液体药品

D．闻气体的气味