如图2所示，倾角为30⁰的直角三角形底边长为2，底边处在水平位置，斜边为光滑绝缘导轨。现在底边中点0处固定一正电荷Q，让一个质量为m、电荷量为q的负电荷的质点从斜面顶端A沿斜边滑下，滑到斜边的垂足D时速度为v.

(1)在质点运动中不发生变化的是(  )

A．重力势能

B．电势能与重力势能之和

C．动能和重力势能之和

D．动能、重力势能、电势能三者之和(2)该质点滑到非常接近斜边底端C时速率v_c为多少?．

Future Computer Trends:
The components of a PC will be built into the (6) and large plasma or electroluminescent flat panel display hanging on a partition wall will act as both a (7) and videophone display.

A. desk B. monitor C. built D. hard

A high resolution, touch sensitive LCD (8) into desktop will allow pan-based pointing and data input. In the home, meanwhile, computers will become as ubiquitous as TVs.
Computer interfaces will be far friendlier than (9) graphical user interfaces (GUI) of today. Computers will use "human interfaces" based on multimedia.
RISC microprocessors will finally obliterate the ever thinning gap between workstations and PCs. Similar advances in nonvolatile flash memory will lead to the replacement of magnetic (10) disks with electronic "silicon disks".