A:若撤去F1,甲的加速度一定增大
B:若撤去F2,乙的加速度一定增大
C:若撤去F1,绳的拉力一定减小
D:若撤去F2,绳的拉力一定减小
如图,在Rt△ABC中,∠ACB=90°,D,E,F分别是AB,BC,CA的中点,若CD=5cm,则EF为( )
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