题干

2015年12月1日世界蹦床锦标赛在丹麦欧登塞落幕,中国队以8金3银2铜领跑奖牌榜.关于运动员从图所示的最高点下落到最低点的过程中(不计空气阻力的影响),下列说法中正确的是(   )

A:  一直做加速运动

B:在最低点时受力平衡

C:接触到蹦床时开始减速

D:所受重力等于弹力时速度最大

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D

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    The Double Ninth Festival

    The Double Ninth Festival, also named the “Chong Yang Festival”, is celebrated on the ninth day of the ninth month of the Chinese lunar calendar.

    The festival began as early as the Warring States Period (475-221 BC). In ancient time, numbers were mysterious and were divided into yin and yang. Yin means something of darkness and yang means life and brightness. The number nine is regarded as yang. The ninth day of the ninth month is a double yang day, so it is called “Chong Yang Festival”. (Chong means “repeat” in Chinese)

    People always climb mountains and drink chrysanthemum wine on the Double Ninth Festival. It is hard to say when the customs were created. But there are many stories which are closely related. As recorded in a historical book of the sixth century, in ancient times, there lived a man named Huang Jing. He was learning the magic arts from Fei Changfang. One day, they were climbing a mountain. Fei Changfang suddenly stopped and looked very upset. He said to Huang Jing, “On the ninth day of the ninth lunar month, a big trouble will come to your hometown”. You must go home immediately. Remember to make a red bag for each one of your family members and leave home quickly and climb to the top of a mountain. Most importantly, you must all drink some chrysanthemum wine. Only by doing so can your family members avoid the big trouble.

    On hearing this, Huang Jing rushed home and asked his family to do exactly as his teacher said. The whole family climbed a nearby mountain and did not return until the evening. When they got back home, they found all their animals dead, including chickens, sheep, dogs and so on.

    Since then, climbing a mountain and drinking chrysanthemum wine became the traditional activities of the Double Ninth Festival, to avoid evil spirits and bad luck. Nowadays, the Double Ninth Festival is also a time for family get-togethers to do some exercise as well as enjoy the autumn scenery.