A:that, that
B:Which, which
C:that, which
D:which, that
一根长为l的丝线吊着一质量为m,带电荷量为q的小球静止在水平向右的匀强电场中,如图所示,丝线与竖直方向成37°角,先突然将该电场方向变为向下且大小不变,不考虑因电场的改变而带来的其它影响(重力加速度为g,sin37°=0.6,cos37°=0.8)求:
—Oh, _______ You're kidding.
飞机在平直跑道上由静止开始匀加速起飞,经20s离地时行驶距离为1200m,求: