A:KNO3(NaCl):蒸发结晶
B:CO(CO2):点燃
C:FeSO4溶液(CuSO4溶液):过量的铁,过滤
D:CaCO3(CaCl2):溶解,过滤,蒸发结晶
面积为S的矩形线圈在磁感应强度为B的匀强磁场中,从中性面起以角速度ω匀速转动,在t时刻线圈磁通量的瞬时值为( )
下面关于摩擦力做功的叙述,正确的是( )
pigs cows cats ducks rabbits sheep
My uncle has a farm. It's big. On the farm, you can see two ____ . There are twenty ____ and eighteen ____ on the farm. You can see eleven ____ , thirteen____ and fifteen____ .