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Before set up his pizza delivery service, he
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If a mother pushes her small son in a swing, giving only a light force each time he returns, eventually he will be swinging quite high. The child can do this for himself by using his legs to increase the motion, but both the mother’s push and the child’s leg movements must occur at the proper moment, or the extent of the swing will not increase. In physics, increasing the swing is increasing the amplitude; the length of the rope on the swing determines its natural oscillation period. This ability of an object to move periodically or to vibrate when stimulated by a force operating in its natural period is called resonance. Resonance is observed many times without consciously thinking about it; for example, one may find an annoying vibration or shimmy in an automobile, caused by a loose engine mount vibrating with increasing amplitude because of an out-of-round tire. The bulge on the tire slaps the pavement with each revolution; at the natural resonance point of the engine mount, it will begin to vibrate. Such vibrations can result in considerable damage if allowed to persist. Another destructive example of resonance is the shattering of a crystal goblet by the production of a musical tone at the natural resonant point of the goblet. The energy of the sound waves causes vibration in the glass; as its amplitude increases, the motion in the glass exceeds the elasticity of the goblet, and it shatters. An instrument called a tachometer makes use of the principle of resonance. It consists of many tiny bars, loosely fastened together and arranged so that each bar can slide independently of the others. Movement of the bars causes changes in a dial. When placed next to a rotating motor or engine, the tachometer picks up slight vibrations which are transferred to the resonant bars. These bars begin to move, and the resulting dial may be read to find the revolutions per minute of the motor very quickly. A tachometer is an instrument that uses resonance to determine ______.
When we think about addiction to drugs or alcohol, we frequently focus on negative aspects, ignoring the pleasures that accompany drinking or drug-taking. (21) the essence of any serious addiction is a pursuit of pleasure, a search for a "high" that normal life does not (22) . It is only the inability to function (23) the addictive substance that is dismaying, the dependence of the organism upon a certain experience and a(n) (24) inability to function normally without it. Thus a person will take two or three (25) at the end of the day not merely for the pleasure drinking provides, but also because he "doesn’t feel (26) " without them. (27) does not merely pursue a pleasurable experience and need to (28) it in order to function normally. He needs to repeat it again and again. Something about that particular experience makes life without it (29) complete. Other potentially pleasurable experiences axe no longer possible, (30) under the spell of the addictive experience, his life is peculiarly (31) . The addict craves an experience and yet he is never really satisfied. The organism may be (32) sated, but soon it begins to crave again. Finally a serious addiction is (33) a harmless pursuit of pleasure by its distinctly destructive elements. A heroin addict, for instance, leads a (34) life: his increasing need for heroin in increasing doses prevents him from Working, from maintaining relationships, from developing in human ways. (35) an alcoholic’s life is narrowed and dehumanized by his dependence on alcohol.
关于妊娠期贫血的防治正确的是
If a mother pushes her small son in a swing, giving only a light force each time he returns, eventually he will be swinging quite high. The child can do this for himself by using his legs to increase the motion, but both the mother’s push and the child’s leg movements must occur at the proper moment, or the extent of the swing will not increase. In physics, increasing the swing is increasing the amplitude; the length of the rope on the swing determines its natural oscillation period. This ability of an object to move periodically or to vibrate when stimulated by a force operating in its natural period is called resonance. Resonance is observed many times without consciously thinking about it; for example, one may find an annoying vibration or shimmy in an automobile, caused by a loose engine mount vibrating with increasing amplitude because of an out-of-round tire. The bulge on the tire slaps the pavement with each revolution; at the natural resonance point of the engine mount, it will begin to vibrate. Such vibrations can result in considerable damage if allowed to persist. Another destructive example of resonance is the shattering of a crystal goblet by the production of a musical tone at the natural resonant point of the goblet. The energy of the sound waves causes vibration in the glass; as its amplitude increases, the motion in the glass exceeds the elasticity of the goblet, and it shatters. An instrument called a tachometer makes use of the principle of resonance. It consists of many tiny bars, loosely fastened together and arranged so that each bar can slide independently of the others. Movement of the bars causes changes in a dial. When placed next to a rotating motor or engine, the tachometer picks up slight vibrations which are transferred to the resonant bars. These bars begin to move, and the resulting dial may be read to find the revolutions per minute of the motor very quickly. An annoying vibration can be caused at the natural resonance of the car’s engine mount ______.
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