地心引力與離心力
Sir Isaac Newton is considered to be one of the greatest mathematicians of all time, developing laws of classical physics such as the three basic laws of motion.
牛頓被視為歷史上最偉大的數學家之一，提出三大運動定律等古典物理學原理。
be considered (to be)=被視為~=be regarded or seen asHe is considered a potential client of our company.mathematician(n.)數學家of all time=有史以來basic(adj.)基本的;基礎的
Here we will focus on the first law of motion, which states: “An object at rest stays at rest and an object in motion stays in motion at the same speed and in the same direction unless an external force influences it.”
本文將集中討論第一運動定律，該定律提到，靜止的物體將保持不動；除非受到外力影響，不然移動中的物體會以同樣的速度往同一個方向繼續移動。
focus on sth.=集中在...;聚焦在...at rest=處於靜止不動或休息的狀態Meditation can help to put our minds at rest.in motion=處於移動的狀態external(adj.)來自外部的internal(adj.)來自內部的The ointment is for external use only.force(n.)力;力量the military (armed) forces=武力;軍力The flood smashed the dam with great force.influence(v.)(n.)影響(力)
In other words, an object tends to keep doing what it is already doing, unless something—an external force—causes it to change.
換言之，除非有外力改變移動速度或方向，否則物體的移動不會有變化。
tend to RV=往往~cause sth. to RV=導致某事物...
To demonstrate this law, you can imagine a ball being thrown upwards in outer space and on Earth.
為說明第一運動定律，可以想像一顆球在外太空與在地球上往上拋。
demonstrate(v.)示範;演示The teacher demonstrated how to draw on a computer.imagine(v.)想像upwards(adv.)向上地downwards(adv.)向下地
In outer space, the ball will continue moving upwards in the same way it was thrown.
在外太空的球會照著一開始拋的方向繼續往上移動，
continue to RV=continue V-ing=繼續做某事
On Earth, that ball would quickly fall back down to the ground.
而地球上的球則會迅速落地。
fall down=掉落
The reason for this is that in space, there is no external force influencing the ball.
原因是，外太空沒有外力影響那顆球的移動，
reason(n.)原因;理由
On Earth, gravity is the external force that is pulling the ball back down towards the center of the Earth.
而在地球上有地心引力，會把球往地心拉下去。
gravity(n.)地心引力;重力The gravity of a black hole is so strong that even light cannot escape.center(n.)中心;中央