题干

小球P和Q用不可伸长的轻绳悬挂在天花板上,P球的质量大于Q球的质量,悬挂P球的绳比悬挂Q球的绳短.将两球拉起,使两绳均被水平拉直,如图所示.将两球由静止释放.在各自轨迹的最低点,(  )

A:P球的速度一定大于Q球的速度

B:P球的动能一定小于Q球的动能

C:P球所受绳的拉力一定大于Q球所受绳的拉力

D:P球的向心加速度一定小于Q球的向心加速度

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答案(点此获取答案解析)

C

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The word that has changed the world

Apple is one of the most popular fruits in our life, and people eat apples every day. But thereare 1apples that are especially important to the history of our human beings and they have changed the whole world.
Long long ago when the world just started, apple was a forbidden  2in the Garden of Eden, however, a girl named Eve stole and ate it. Unfortunately, she was discovered by God, and was driven away 3 the Garden together with a boy called Adam. After they 4 the garden, Adam and Eve had their own babies and 5 the ancestors of all of us. This is the beginning of our world, history6morality.
In the Autumn of 1665, there 7 a young man sitting under an apple tree in his garden. His name was Newton. While he was thinking of one problem, suddenly, an apple dropped down from the tree and fell on his head.8 this, Newton discovered gravitation on that day and his new idea of science made people really 9 and happy, also he changed our opinions about nature and the way 10 we think, then people began to11what science was at that time.
And today, Jobs Steve, this crazy old man changed the world by his apple products. For example, iPhones12 be found 13 in the street, young people feel cool when they use this kind of new high-tech product. Don't you think14apple products have become a symbol of our time? As Jobs Steve often said he was born to change the world and he made it.15 he has died, people remember him and miss him, because he made our life more colorful and amazing.