12,13,15,18,22()
A.25
B.27
C.30
D.34
参考答案:B
质量为m,带电荷量为+q的小球从距离地面高为h处以一定的初速度水平抛出,在距抛出点水平距离L处,有一根管口比小球直径略大的竖直细管,管的上口距离地面h/2。为使小球能无碰撞的通过管子,可以在管口上方的整个区域内加上水平方向的匀强电场,如图所示,则下列说法中正确的是
A.所加电场方向应该水平向右
B.小球平抛的水平初速度大小为L
C.所加电场的电场强度为
D.小球落地的动能为mgh+
Which of the following is NOT a contributory factor to thermoregulation in the preterm neonate()
A. Immature central nervous system (CNS).
B. Large skin surface area.
C. Lack of subcutaneous (SC) and brown fat.
D. Tendency toward capillary fragility.