One day, Mr. Black went into a restaurant. He put his coat on a chair near the door. There was nothing in the pockets of his coat. After he had his meal, he went to take his coat back. He found there was much money in one of his pockets. “Whose is this?” he thought. He saw a waiter near the door. So Mr. Black said to him, “Somebody put a lot of money in my coat. I have no time to wait for him. I have to go. Take it, please. When he comes back, give it to him.” The waiter took it and went away. At the moment, another man came with a coat just like Mr. Black's. “I'm sorry,” said the man. “I took your coat and you got mine. Please give me my coat and the money. ” Mr. Black answered, “I gave it to the waiter. He'll give it to you. ”

    Mr. Black called the manager（经理）, but the manager said, “We have no waiters here. We only have waitresses（女服务员）. He must be a thief（小偷）.”

如图所示，物块A和B，分别系在一条跨过定滑轮的软绳两端，放手后，A向下B向上加速运动，现要利用此装置验证机械能守恒定律．

——Where is the new student       ?   

——America.