题干

如图,有三个质量相等、分别带正电、负电和不带电的粒子从两水平放置的金属板左侧中央以相同水平初速度v0先后射入电场中,最后分别打在正极板ABC 处,则(     )

A:三种粒子在电场中运动时间相同  

B:三种粒子到达正极板时动能EKC>EKB>EKA

C:三种粒子在电场中的加速度为aA>aB>aC

D:落在C 处的粒子带负电,落在B 处的粒子不带电,落在A 处粒子带正电

上一题 下一题 0.0难度 选择题 更新时间:2018-11-30 03:24:55

答案(点此获取答案解析)

C

同类题5

阅读理解

    Green tree ants are important builders in the rainforest. They're like the worker bees of the ant world. The native forest of Thala Beach Nature Reserve is the natural home of these insects.

    They climb all over the tree that contains their nest and protect it from enemies with great fierceness. The ants are often in the fruiting trees of Tropical North Queensland. When an animal tries to help themselves to some tasty fruit, they find themselves attacked by a powerful, frightening army of green tree ants! Their bite is not very painful but many ants attacking at the same time can be extremely uncomfortable.

    The nests are large and constructed by sticking the leaves at the end of branches together to create a home looking roughly like a globe. Most of the nest construction and weaving is conducted at night. A mature colony of green tree ants can hold as many as 100,000 to 500,000 workers and may include as many as 12 trees and contain as any as 150 nests. Green tree ant colonies have one queen and a colony can live up to eight years.

    However, the ants are so busy that they fail to spot a dishonest figure. There is a spider called the Salticid spider, or the jumping spider, as they are sometimes referred to, which has excellent eyesight and is only active during daylight, weaving a protective covering of silk to spend the night in. Interestingly, the Salticid spider does not look like a green tree ant. Instead, it chemically copies green tree ants' smell. Effectively pretending to be an ant, it goes into the green tree ants' nest, enters the nursery and feasts on their babies. Green tree ants don't have good eyesight and smell everything with their antennae (two long thin parts on an ant's head). Therefore, the ants think the spider is another ant and ignore its presence within the nest.

    Next time, as you wander around Thala's native forest, keep an eye out for these busy little creatures. Look up into the trees and you'll likely spot their nests.