题干

小东学完摩擦力的知识后,发现当物体受到向前的拉力或推力时,物体向前运动,这时物体就会受到向后的摩擦力的作用,因此小东认为物体所受摩擦力的方向总与物体所受拉力或推力的方向相反。请用身边的物品设计一个实验,证明小东的结论不正确。请写出实验器材、实验过程及结论。

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答案(点此获取答案解析)

答:器材:购物车
过程:向前推购物车,车向前运动,用一个向后的力拉车,车由于具有惯性继续向前运动
结论:车向前运动过程中,车所受的摩擦力的方向与拉力的方向一致。

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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.