题目内容

"When a baseball is hit straight at an outfielder, he cannot quickly judge the angle of the scent and the distance the ball will travel," says Robert Adair, a physicist at Yale University. If he relied purely upon visual information, the fielder would have to wait for about one-and-a-half seconds before he could tell accurately if the pitcher hit the ball long or short. By this time the ball may have travelled too far for him to reach it in time.
To stand a fighting chance of catching it, according to Adair, fielders must listen to the sound the ball hitting the bat to judge how far it will travel. There is anecdotal evidence to support this, he says. A former centre fielder told Adair: "If I heard a crack I ran out, if I heard a clunk, I ran in."
To test his hypothesis, Adair calculated how quickly a fielder could change direction if he had misjudged whether the ball was going long or short. The difference between the "crack" and "clunk” can he explained by how well the batter has hit the ball, and could mean a difference in running distance of as much as 30 metres, he told delegates at a meeting of the Acoustical Society of America in Chicago last week.
Scientists already knew that to hit a ball long the batter must strike it somewhere near the vibrational node of the bat, known as the sweet spot. Balls hit on the sweet spot generate fewer energy-sapping vibrations in the bat, allowing greater energy transfer to the ball. Conversely, mishit balls make the bat vibrate strongly and so do not travel as far.
Adair is quick to point out that this only applies to wooden bats, which are used in major league baseball. Aluminum bats, on the other hand, tend to produce a fairly uniform. "ping” sound regardless of where you hit them.
According to Robert Adair, why can't an outfielder rely purely on visual information?

A. Because it may take longer time for him to exert judgment.
Because the ball may change directions during flight.
C. Because the ball may be hit either long or short.
D. Because light travels faster than sound.

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更多问题

From paragraph 3 we can infer that a "crack" may mean ______.

A. a long ball
B. a short ball
C. a good ball
D. a mishit ball

电缆的地下埋设要求中,在直埋电缆直线段每隔()m处、电缆接头处、转角处和进入建筑物等处,均应设置明显的方位标志或标桩。

A. 10~50
B. 50~100
C. 100~150
D. 150~200

If the bat vibrates very little, ______.

A. the fielder is unable to catch the sound
B. the ball will travel to a short distance
C. the ball may receive greater energy
D. the fielder should quickly run in

Children model themselves largely on their parents. They do so mainly through identification. Children identify 【C1】______ a parent when they believe they have the qualities and feelings that are 【C2】______ of that parent. The things parents do and say--and the 【C3】______ they do and say to them-- strongly influence a child's 【C4】______ .
A parent's actions 【C5】______ affect the self image that a child forms 【C6】______ identification. Children who see mainly positive qualities in their 【C7】______ will likely learn to see themselves in a positive way. Children who observe chiefly 【C8】______ qualities in their parents will have difficulty 【C9】______ positive qualities in themselves. Children may 【C10】______ their self image, however, as they become increasingly 【C11】______ by peer groups:
In the case of a dramatic change in family relations, the 【C12】______ of an activity or experience depends on how the child interprets it. Children interpret such events according to their established attitudes and previous training. Children who know they are loved can, 【C13】______ , accept the divorce of their parents or a parent's early 【C14】______ . But if children feel unloved, they may interpret such events 【C15】______ a sign of rejection or punishment.
【C1】______

A. to
B. with
C. around
D. for

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