5.2 胎体力

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  胎体力

  

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  Jupiter's moons and ring materials follow all the laws of physics , including centripetal force and .
  ::木星的卫星和环状材料 都遵循物理定律 包括三子体力和

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  Centripetal Force
  ::胎体力

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  Centripetal force is, simply, the force that causes centripetal acceleration. Objects that move in uniform all have an toward the center of the circle and therefore, they must also suffer a force toward the center of the circle.  That force is the centripetal force. For orbiting satellites, such as the moon orbiting the earth or the earth orbiting the sun, the centripetal force is produced by gravity. When an Olympic hammer thrower whirls a massive ball on a chain, the centripetal force is created by the athlete and transmitted by the chain.
  ::中子力只是引起子宫加速的力。 穿制服移动的物体都向圆圈中心方向移动, 因此, 它们也必须承受向圆圈中心方向的力。 该力是三子力。 对于环绕卫星轨道运行的卫星, 如环绕地球的月球或环绕太阳的地球, 子宫力是由重力产生的。 当奥林匹克锤子扔出一个巨大的球在链子上, 球体的力量是由运动员创造的, 并且由链子传递的。

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  Newton’s second law shows the relationship between force and acceleration, $\begin{array}{r}F=ma\end{array}$ .  Since we have formulas expressing the relationships for centripetal acceleration, they can easily be altered to show the relationships for centripetal force.
  ::牛顿的第二项法律显示了力和加速力之间的关系,F=ma。 由于我们有表达子宫加速力关系的公式,因此它们很容易被修改,以显示子宫加速力的关系。

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  $\begin{array}{r}{a}_c=\frac{v^2}{r}andF=maso{F}_c=\frac{m{v}^2}{r}\end{array}$
  ::ac=v2r和F=ma so Fc=mv2r

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  and
  ::和

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  $\begin{array}{r}{a}_c=\frac{4{\pi }^{2}r}{T^2}\text{so}{F}_c=\frac{4{\pi }^{2}rm}{T^2}\end{array}$
  ::ac=42rT2 so Fc=42rmT2

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  Practice applying centripetal force on a hockey puck so that it moves in a circle in the simulation below. Be sure to apply the equations above to help you solve for the magnitude of the centripetal force and the initial of the puck:
  ::练习在曲棍球球上应用百分位力使其在下面模拟的圆圈中移动。 请使用上面的方程式帮助您解析百分位力的大小和圆球的首字母 :

   

   

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  Common Misconceptions
  ::常见误解

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  Many people incorrectly use the term centrifugal force  instead of centripetal force . Often, you will hear the term centrifugal force used to describe the outward force pushing an object away from the center of a circle. In reality, however, centrifugal forces are inertial, or fictional, forces. They only exist in the frame of reference of the object that is moving and, even then, are theoretical. Physicists dealing in a moving frame of reference use centrifugal forces to ease calculations.
  ::许多人错误地使用离心力而不是离子力。通常,你会听到用来描述将物体从圆圈中心推开的外力的离心力。但实际上,离心力是惯性或虚构的力。它们只存在于移动对象的参照框架之内,即便在当时,它们也是理论上的。在移动参照框架内处理的物理学家使用离心力来减轻计算。

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  For a great explanation of the difference between centrifugal and centripetal force, see this video:
  ::关于离心力和子宫骨力的区别的深刻解释,请看这段录像:

   

   

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  Have you ever played tetherball? It’s a really fun game and a great example of how a centripetal force causes an object to move in a circle. The motion of the ball is governed by two forces - gravity and tension - that combine to generate a net centripetal force. Use the following simulation to adjust the ball mass, cable length and ball in a tetherball match to learn more:
  ::玩过绳子球吗? 这是一个非常有趣的游戏, 并且是一个极好的例子, 说明三子体的力量如何促使物体在圆圈中移动。 球的运动由两种力量( 重力和紧张力) —— 重力和紧张力—— 调节, 结合产生纯子球力。 使用以下模拟来调整球质量、 电缆长度和球在绳子球比赛中的比对来学习更多 :

   

   

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  Further Reading
  ::继续阅读

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  Summary
  ::摘要

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  • Centripetal force is the force that causes centripetal acceleration. 
    ::中子力是造成子宫加速的力。
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  • Equations for centripetal force are  $\begin{array}{r}{F}_c=\frac{m{v}^2}{r}\end{array}$  and  $\begin{array}{r}{F}_c=\frac{4{\pi }^{2}rm}{T^2}\end{array}$  .
    ::中子力的等量为Fc=mv2r和Fc=42rmT2。

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  Review
  ::回顾

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  1. A runner with a mass of 78.6 kg, moving at a speed of 8.8 m/s, rounds a bend with a radius of 25 m.  What is the centripetal force needed to keep this runner on the curve and what supplies this force?
     ::以8.8米/秒的速度移动的、质量为78.6公斤的跑者,在半径为25米的弯道上转弯。 将跑者保持在曲线上所需的子宫力是什么? 是什么提供了这种力量?
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  2. A 1000. kg car rounds a curve of 50.0 m radius on a flat road with a speed of 14.0 m/s. 
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     1. Will the car make the turn successfully if the pavement is dry and the coefficient of friction is 0.60?
        ::如果路面干燥,摩擦系数为0.60,汽车会成功转弯吗?
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     2. Will the car make the turn successfully if the pavement is wet and the coefficient of friction is 0.20?
        ::如果路面是湿的,摩擦系数是0.20,车会成功转弯吗?
     
     ::A1000公斤汽车在平坦公路上绕行50米半径的曲线,速度为14.0米/秒。 如果路面干燥,摩擦系数为0.60,车能成功转弯吗?如果路面湿透,摩擦系数为0.20,车能成功转弯吗?
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  3. An 0.500 kg object tied to a string is swung around a person’s head in a horizontal circle.  The length of the string is 1.00 m and the maximum force the string can withstand without breaking is 25.0 N.  What is the maximum speed the object may be swung without breaking the string?
     ::与字符串捆绑在一起的0.500公斤物体在水平圆上缠绕着一个人的头部。字符串的长度为1米,而字符串在不折断的情况下能够承受的最大强度为25.0牛顿。该物体在不折断字符串的情况下能够承受的最大速度是多少?