问题 选择题

如图所示,两个底面积不同的圆柱形容器甲和乙,容器足够高,分别盛有水和酒精(ρ>ρ酒精),且两种液体对容器底部的压强相等。一定能使水对容器底部的压强大于酒精对容器底部压强的方法是                                          (    )

A 倒入相同质量的水和酒精

B 倒入相同体积的水和酒

C 抽出相同质量的水和酒精

D 抽出相同体积的水和酒精

答案

答案:C

∵甲和乙是圆柱形容器,

∴对容器底的压力:F=ps=ρghs=ρgV=mg=G;

∵S>S

对容器底的压强:p=p

∴m>m酒精

A、倒入相同质量的水和酒精,增加的压力相等,底面积左边容器的大,所以左边容器增加的压强小,会使水对容器底部的压强小于酒精对容器底部压强,不符合题意;

B、倒入相同体积的水和酒精,

∵ρ>ρ酒精

∴m>m酒精

这样可以使水对容器底的增加的压力大于酒精对容器底增加的压力,底面积左边容器的大,不好确定哪个增加的压强多,不能确定水对容器底部的压强和酒精对容器底部压强的关系,不符合题意;

C、抽出相同质量的水和酒精,减小的压力相等,底面积左边容器的大,所以左边容器减小的压强小,会使水对容器底部的压强大于酒精对容器底部压强,符合题意;

D、抽出相同体积的水和酒精,

∵ρ>ρ酒精

∴m>m酒精

这样可以使水对容器底的减小的压力大于酒精对容器底减小的压力,底面积左边容器的大,不好确定哪个减小的压强多,不能确定水对容器底部的压强和酒精对容器底部压强的关系,不符合题意;

故选C.

名词解释
单项选择题

Young girls at high risk for depression appear to have a malfunctioning reward system in their brains, a new study suggests. The finding comes from research that (1) a high-risk group of 13 girls, aged 10 to 14, who were not depressed but had mothers who (2) recurrent depression and a low-risk group of 13 girls with no (3) or family history of depression. Both groups were given MRI brain (4) while completing a task that could (5) either reward or punishment.

(6) with girls in the low-risk group, those in the high-risk group had (7) neural responses during both anticipation and receipt of the reward. (8) , the high-risk girls showed no (9) in an area of the brain called the dorsal anterior cingulated cortex (背侧前扣带皮质), believed to play a role in (10) past experiences to assist learning.

The high-risk girls did have greater activation of this brain area (11) receiving punishment, compared with the other girls. The researchers said that this suggests that high-risk girls have easier time (12) information about loss and punishment than information about reward and pleasure.

"Considered together with reduced activation in the striatal (纹状体的) areas commonly observed (13) reward, it seems that the reward-processing system is critically (14) in daughters who are at elevated risk for depression, (15) they have not yet experienced a depressive (16) ," wrote Ian H. Gotlib, of Stanford University, and his colleagues. " (17) , longitudinal studies are needed to determine whether the anomalous activations (18) in this study during the processing of (19) and losses are associated with the (20) onset of depression," they concluded. The study was published in the April of the Archives of General Psychiatry.

14()

A.repaired

B.impaired

C.healed

D.damaged