曲柄OC以匀角速w 0绕轴O转动,并带动椭圆规-|||-尺AB 做平面运动。若 t=0 时,-|||-varphi =0, overline (OC)=overline (AC)=overline (BC)=r 则当 varphi =(45)^circ 时候-|||-滑块A的速度大小为 __ 。-|||-A、 sqrt (2)rcos (theta )_(0)-|||-B、rw0-|||-C、2rUND0-|||-D、 dfrac (sqrt {2)ra(b)_(0)}(2)-|||-y-|||-4-|||-A B-|||-b-|||-C-|||-φ 2 L x-|||-O-|||-7m? DBAC