题干

如图,质量为m的物体在水平传送带上由静止释放,传送带由电动机带动,始终保持以恒定的速度v匀速运动,物体与传送带间的动摩擦系数为,物体最后能保持与传送带相对静止。对于物体从开始释放到相对静止的这一过程中,下列说法正确的是(    )

A:电动机增加的功率为

B:摩擦力对物体做的功大于

C:传送带克服摩擦力做的功为

D:电动机多做的功为

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A

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If music makes you smarter and exercise helps you to think, surely exercising to music can turn you into a clever person.

A team of scientists from Ohio State University did experiments on 33 volunteers who were getting better from heart disease after operations. They found those volunteers who exercised while listening to Italian musician Antonio Vivaldi's The Four Seasons did much better on language ability tests than without music. It is also used in medical fields for patients who have had head hurts because of its moderate tempo (舒缓的节拍).

“Exercise seems to cause positive changes in the nerve (神经) system and these changes may improve the learning ability of people with heart disease,” said the psychologist Charles Emery, who led the study. “And listening to music is thought to enhance understanding. We just wanted to put the two results together,” he added.

The volunteers said they felt better emotionally and physically after exercising with or without music. But their improvement on the test doubled after listening to music during exercise. Scientists have proved that music can be good for health and education. It helps reduce stress and sadness, encourage relaxation or sleep, wake up the body and improve memory and thoughts.

Scientists have been studying the results of exercise to music on learning and understanding since the early 1950s. A study showed that students who listened to Mozart's violin pieces and exercised went on to get higher marks in an IQ test. With important exams drawing near, your parents will not probably allow you to listen to music or play sports. But perhaps now you have good reasons to argue with them.