题干

物体自由下落的高度h(米)和下落时间t(秒)的关系是:在地球上大约是h=4.9t2,在月球上大约是h=0.8t2,当h=20米时,

(1)物体在地球上和在月球上自由下落的时间各是多少?

(2)物体在哪里下落得快?

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答案(点此获取答案解析)

解:(1)h=20米时,地球上,4.9t2=20,解得t=10
2
7
,月球上,0.8t2=20,解得t=5;(2)在地球上的速度=

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    Tang Dynasty poets sang for about three centuries in different tones. There were many famous poets living in the Tang period such as Li Bai, Du Fu, Bai Juyi and Li Shangyin. Poems of the Tang Dynasty edited in the Qing Dynasty is a collection of about 48,900 poems that were written by over 2,200 poets. But it didn't cover all the poems of the Tang Dynasty.

    During the Tang Dynasty, poems were recited when lovers walked under the moonlight. Poems were also recited when soldiers fought on the battlefield. People recited them in the open air or at temple fairs.

    In the Tang Dynasty scholars had to be poets. Their readers were not only people of high social position but also common people. Poets recited poems; women singers sang poems and other ranks of people, including old women and children, read Tang poems. This atmosphere affected foreigners who visited the country at that time. As a result, Tang poetry was introduced to some adjacent countries, like Japan and Vietnam.

    Tang poetry is a most brilliant page in the history of ancient Chinese literature. It's a miracle in the cultural history of mankind. The Tang Dynasty was a powerful empire with a vast territory. It inherited Chinese civilization that went back to ancient times, and was combined with the best of other cultures and adopted the benefits of other nations in the world. Tang poetry wasn't the only spiritual wealth created by the Tang Dynasty people. Philosophy and religion, handwriting and painting and music and dance all gained new peaks of development. Tang poetry, however, was the jewel in the crown and its greatest achievement.