宇宙中两颗星体依靠万有引力相互绕转运动,距离保持为r,且质量不同,即m1不等于m2.以星球2为参考系,星球1的向心力F=4π^2*m(1)*r/T(1)^2,星球2的向心力F=4π^2*m(2)*r/T(2)^2,由牛顿第二定律得两个向心力相等,则推出m(1):m(2)=T(1)^2:T(2)^2,根据m(1)不等于m(2),所以T(1)不等于T(2),T是周期,所以在两个参考系中,同样的圆周运动,表现出的被参考对象的运动周期不同.为什么?

MF4型手提式干粉灭火器的灭火参考面积是（）m2. A: 1.5 B: 1.8 C: 2 D: 2.5

Which of the following statements is correct? ( ) A: All items that are included in M1 are included also in M2. B: All items that are included in M2 are included also in M1. C: Credit cards are included in both M1 and M2. D: Savings deposits are included in both M1 and M2.

Credit cards () A: are<br/>included in M1 but not M2. B: are<br/>included in M1 and M2. C: are<br/>included in M2 but not M1 D: are<br/>not included in any measure of the money supply.

‍输出上列表格M的第2行‍ A: M[[2]] B: M[2] C: M{[2]} D: M[{2}]

压力的单位用Pa表示，1Pa＝1N/m2.

【填空题】古山三村项目7#楼建筑面积为 ?其中 地下室地下二层建筑面积为 m2,地下一层建筑面积为 m2,一层建筑面积是 m2,二层建筑面积是 m2,三层建筑面积是 m2,四层建筑面积是 m2,五层建筑面积是 m2,6-23层建筑面积是 m2,12.20层(不含已算)建筑面积是 m2,8.16.24层建筑面积是 m2,25层建筑面积是 m2.屋面及机房层建筑面积是 m2. 7#楼2015.7.29.dwg

一个沿轴线方向均匀磁化的磁棒，直径30 mm，长60 mm，磁矩为1.0×104 A·m2．棒侧表面上磁化电流密度为2.36×108 A/m。

刚性屋面分仓缝的控制面积为__________m2.

如果向东走2<br/>m记为+2<br/>m,则向西走3<br/>m可记为(<br/>) A: +3 m B: +2 m C: -3 m D: -2 m