lession 3.pdf - 3.1 Gravity and Forces Gravity is one of the universal forces that governs the motions of celestial bodies So how do we define a force

# lession 3.pdf - 3.1 Gravity and Forces Gravity is one of...

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3.1 Gravity and Forces Gravity is one of the universal forces that governs the motions of celestial bodies. So how do we define a force ? We are all familiar with push and pull. This is an interaction that causes your body to accelerate. Acceleration is defined in terms of changing speed. When you accelerate your speed increases. When you decelerate your speed decreases. Newton was the first one to quantify the concept of force in his famous three laws. 3.1 重༒ʛ力和༒ʛ力 重༒ʛ力是ཀ支配天体运动的普遍༒ʛ力Ǐ量之ༀ一。 那么我们如何定义༒ʛ力呢？ 我们都熟悉推拉。 这是ༀ一种相互作ཤ用，使您的身体加速。 加速度是根据变化的速度定义的。 当您加速时，速度会增加。 减速时，速度 会降低。 ཛྷ牛顿是他著名的三定ྋ律中第ༀ一个Ǐ量化༒ʛ力概念的༈人。 3.2 Force According to Newton’s laws a body continues in uniform motion, or at rest, unless a force acts on it. (Newton’s First Law). A force applied to a body causes it to accelerate by an amount given by the force divided by the mass of the body (Newton's Second Law). Acceleration is defined as the change in speed in a given time. Force is measured in units called Newtons. A force of one Newton causes a mass of one kilogram to accelerate with an acceleration equal to 1 metre per second per second. For completeness lets mention Newton's third law. It states that for every force there is an equal and opposite force. If you push the table with your hand, it will push back on you with this opposing force as hard as you are pushing on it. 3.2 ༒ʛ力 根据ཛྷ牛顿定ྋ律，除ྮ非有༒ʛ力作ཤ用于身体，否则身体将继续以匀速运动或处于静ཌ止 状态。 （ཛྷ牛顿第ༀ一定ྋ律）。

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