题目

TOKYO, JAPAN--What do you do when you see a cockroach (蟑螂）？ Do you hit it with a newspaper? Do you step on it? When researchers at Tokyo University see a cockroach, they take the remote control and make the cockroach turn around, run left or right, or go forward. These scientists are changing the cockroaches into robots. Each cockroach has a very small pack that has in it a microprocessor(微处理器）.Then researchers can send signals from the remote control to the pack. The signals control the movements of the cockroaches. Why does anyone want to control a cockroach? “I足够长的木板质量为，沿水平地面做匀减速运动。t=0时刻，在木板上无初速放一质量为的物块，物块与木板、木板与地面间的动摩擦因数相同．分别用和表示木板和物块的速度，下列反映和变化的图线中正确的是