上海新世紀英語高二全部課文及重點詞組

some people estimate yuan’s actual fortune might make him one of the richest people in china. but he doesn’t know for sure himself, for he seems to care for nothing more than his research.
in spite of his busy research work, yuan longpin has managed to keep some hobbies in his spare time, including reading books and listening to music. he enjoys daily motor cycling and sometimes playing the violin.
28. newton’s three important laws
things that move obey certain laws. three important laws of motion were established by isaac newton (1642～1727) (英國物理學家、天文學家和數學家，被公認為有史以來最偉大和影響最深遠的科學家).
newton ⅰ: inertia(慣性定律)
newton’s first law of motion seems simple: objects at rest tend to remain at rest, while moving ones continue to move at a uniform speed in a straight line---unless acted upon by an outside force. this resistance(阻力) to change is called inertia, and it explains a lot of everyday experienced no matter where you happen to live.
one is that when the car or airplane you’re in begins to move, your body is pushed back against the seat. that is, it tends to remain at rest despite the forward-moving force of the vehicle transferred to you through the seat. another aspect of this law shows that the normal courses for freely moving objects is a straight line. that explains why, when you whirl(迅速旋轉) something around your head---such as a ball on a string---and then let it go, the ball flies straight. it neither keeps circling your head nor does it move off in a sweeping(做大幅度弧線形運動的) curve(曲線).
newton ⅱ: f=ma
newton’s second law relates the amount of force needed to move an object to the object’s mass and tits acceleration(加速度).
push a child in a swing, or ride a planet around the sun, and you’re using newton’s second law of motion, which states that whenever you want to change the speed or direction of something, you have to apply an appropriate force. the bigger the mass or the larger the intended acceleration, the greater the necessary force. this law’s formula allows engineers to calculate what’s required to launch a jet fighter(噴氣式戰斗機) from an aircraft carrier(航空母艦), or how strong a seat belt must be to restrain(抑制，控制), say, a 160-pound person when his car stops suddenly while travelling at 60 mph.
newton ⅲ: equal and opposite(作用力與反作用力)
all objects, moving or at rest, obey newton’s third law of motion, which holds that in nature, unaccompanied(無陪伴的) forces do not exist.
you can’t take a step without applying newton’s third law, which explains that for every action there is an equal and opposite reaction. each time your foot pushes down on the ground, the ground pushes back with the same amount of force pointed in precisely(精確地，準確地) the opposite direction. in fact, it’s the force exerted(施加壓力) by the ground that pushes you along, not the force of your foot.