题干

如图所示,让A橡皮和B橡皮用轻绳相连挂在轻质弹簧下静止不动,A橡皮的质量为m,B橡皮的质量为M,当连接A橡皮、B橡皮的绳子突然断开后,橡皮A上升经某一位置时的速度大小为v,这时橡皮B的下落速度大小为u,在这一段时间里,弹簧的弹力对橡皮A的冲量及B橡皮重力的冲量大小分别为(   )

A:Mv,Mu

B:mv﹣Mu,Mv

C:mv+Mu,Mv

D:mv+mu,Mu

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D

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    One day, Luke Fortune drove from Oregon to Portland, where he parked his car in a paid garage overnight. The next morning, he 1 the car's window had been broken, along with his 2 for the future: His computer was 3 “Everything important to me was on that computer,” said Fortune. “I felt 4.

    Two days after the 5 another young man called Fortune. Masoud Almazrouei was an exchange student from the United Arab Emirates. He'd been 6by a man who said he had a computer for sale. Only $ 200. Almazrouei 7 a computer, so he bought it, took it home, and turned it on. Within seconds, he saw files and photographs. “I wondered who would8 a computer with all of this on it,” he said. “I 9it could be stolen.”Almazrouei found what appeared to be the owner's phone number and called it10

    “He told me the story and said it was his fault. I thought it was a11 I told him if he really had the 12 he should take it to the police.” Fortune said13a police officer called Fortune to say that a man had dropped the computer off and had said he was14He passed on the man's number. Fortune called and thanked Almazrouei and 15paying him a reward of $ 200—the money he was out. Almazrouei 16.

    When a report about the two young men's story made it to the local papers, Almazrouei received a(n)17 from Wim Wiewel, the president of the university where Almazrouei is studying. Impressed with his student's18Wiewel gave Almazrouei a new computer. “We thought since you 19 the computer, we should give you a computer so that you'll have one,” Wiewel told him. “We're very20you.”