11.2 异性痴呆症
Section outline
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At Newton’s Skate Park, Lauren is pushing her twin cousins, Jonathan and Cody, on her skateboard. She has to push hard to get the skateboard started, but once it begins moving, it takes much less effort to keep it rolling over the smooth, flat pavement. In fact, if Lauren tries to stop the rolling skateboard, it may take as much effort to stop it as it did to start it rolling in the first place.
::在牛顿滑板公园,劳伦将她的双胞胎堂兄弟乔纳森和科迪推上滑板。 她必须努力让滑板启动,但一旦滑板开始移动,就更不用再努力让滑板在平滑的平板路面上滚动。 事实上,如果劳伦试图阻止滑板滑板,那么要阻止滑板,可能要像一开始开始滚动一样努力。Q : Why is it harder to start and stop the skateboard than it is to keep it rolling?
::问:为什么开始和停止滑板比继续滚动更难?A : The reason is inertia.
::A:原因是惰性。What Is Inertia?
::什么是因诺琴蒂亚?Inertia is the tendency of an object to resist a change in its motion. All objects have inertia, whether they are stationary or moving. Inertia explains Newton’s first law of motion , which states that an object at rest will remain at rest and an object in motion will stay in motion unless it is acted on by an unbalanced force. That’s why Newton’s first law of motion is sometimes called the law of inertia.
::惰性是物体抵制运动改变的倾向。 所有物体都具有惰性,不管它们是静止的还是移动的。 Inertia解释了牛顿的第一个运动法则,其中规定,休息的物体将保持休息,运动的物体将保持运动,除非以不平衡的力量采取行动。 这就是为什么牛顿的第一个运动法则有时被称为惰性法则。Q : You probably don’t realize it, but you experience inertia all the time, and you don’t have to ride a skateboard. For example, think about what happens when you are riding in a car that stops suddenly. Your body moves forward on the seat and strains against the seat belt. Why does this happen?
::问题:你可能没有意识到这一点,但你总是经历着惰性,也不必骑滑板。 比如,想想当你乘坐一辆突然停车的汽车时会发生什么。 你的身体在座位上向前移动,对安全带施压。 为什么这种情况会发生呢?A : The brakes stop the car but not your body, so your body keeps moving forward because of inertia.
::A:刹车停止了汽车,但不能阻止你的身体,所以你的身体因为惰性而继续前进。Inertia explains why it’s important to always wear a seat belt. Inertia and Mass
::惯性与质量The inertia of an object depends on its mass. Objects with greater mass also have greater inertia. It would be easier for Lauren to push just one of her cousins on her skateboard than both of them. With just one twin, there would be only about half as much mass on the skateboard, so there would be less inertia to overcome.
::物体的惯性取决于其质量。 质量较大的物体的惯性也更大。 Lauren将表兄弟之一推到滑板上比将他们两人推到滑板上要容易得多。 如果只有一个双胞胎,滑板上的惯性将只有一半左右,因此,要克服的惯性将更少。Overcoming Inertia
::克服无电状态To change the motion of an object, inertia must be overcome by an unbalanced force acting on the object. The unbalanced force that starts Lauren’s cousins rolling along on the skateboard is applied by Lauren when she gives it a push. Once an object starts moving, inertia keeps it moving without any additional force being applied. In fact, it won’t stop moving unless another unbalanced force opposes its motion. For example, Lauren can stop the rolling skateboard by moving to the other end and pushing in the opposite direction.
::为了改变物体的动作,惰性必须被在物体上行动的不平衡力量所克服。 Lauren在滑板上开始劳伦表弟们滚动的不平衡力量由她施压时运用。 一旦物体开始移动,惰性就会让它在不施加任何额外武力的情况下继续移动。 事实上,除非另一支不平衡力量反对它的运动,否则它不会停止移动。 比如,Lauren可以通过向另一端移动和向相反的方向推进来阻止滚动滑板。Q : What if Lauren didn’t stop the skateboard in this way? If it remained on a smooth, flat surface, would it just keep rolling forever?
::问:如果劳伦没有以这种方式阻止滑板呢? 如果滑板停留在平滑平坦的表面,它会永远滚动吗?A : The inertia of the moving skateboard would keep it rolling forever if no other unbalanced force opposed its motion. However, another unbalanced force does act on the skateboard
::A:如果没有其他不平衡力量反对滑板动议,移动滑板的惰性将永远保持滑板滚动。 然而,另一支不平衡力量确实在滑板上行动。Q : What other force is acting on the skateboard?
::问:在滑板上还有哪支力量在行动?A : The other force is rolling between the skateboard’s wheels and the ground. The force of friction opposes the motion of the rolling skateboard and would eventually bring it to a stop without any help from Lauren. Friction opposes the motion of all moving objects, so—like the skateboard—all moving objects eventually stop moving even if no other forces oppose their motion.
::一:另一股力量在滑板的轮子和地面之间滚动。 摩擦力量反对滑板运动,最终在没有劳伦任何帮助的情况下阻止滑板运动。 摩擦力量反对所有移动物体的运动,就像滑板一样,所有移动物体最终都停止移动,即使没有其他力量反对它们的行动。Later that day, Jonathan rode his skateboard and did some jumps. You can see him in the picture . When he’s in the air, there is no rolling friction between his wheels and the ground, but another unbalanced force is acting on the skateboard and changing its motion.
::当天晚些时候,乔纳森骑着他的滑板跳了几下。 你可以在照片中看到他。 当他在空中时,他的车轮和地面之间没有滚动摩擦,但另一支不平衡的力量正在滑板上行动并改变运动。Q : What force is acting on the skateboard when it is in the air above the ground? And how will this force change the skateboard’s motion?
::问题:当滑板在地面上空时,是什么力量在滑板上行动? 这场力量将如何改变滑板的动作?A : The force of gravity is acting on the skateboard. It will pull the skateboard back down to the ground. Once it’s on the ground, friction will slow its motion.
::A:重力作用在滑板上。 它会把滑板拉回地面。 一旦滑板落地,摩擦就会减缓运动。Summary
::摘要-
Inertia is the tendency of an object to resist a change in its motion. Because of inertia, a resting object will remain at rest, and a moving object will keep moving.
::惰性是物体抵抗运动变化的倾向。 由于惰性,休息物体将保持休息,移动物体将保持移动。 -
Objects with greater mass have greater inertia.
::质量较大的物体具有较大的惯性。 -
To change the motion of an object, inertia must be overcome by an unbalanced force acting on the object.
::要改变物体的动作,惯性必须通过对物体采取行动的不平衡力量来克服。
Review
::回顾-
What is inertia?
::什么是惯性? -
How does inertia affect the motion of an object?
::惰性如何影响物体的运动? -
What is the relationship between inertia and mass?
::惰性和质量之间的关系是什么? -
Jonathan and Cody’s older brother Josh, who are pictured in the
Figure
, are standing at the top of a half-pipe at Newton’s Skate Park. Gravity is exerting a downward force on the
scooter
, as seen in the picture. Why doesn’t it tip over the edge and start rolling down the side of the half-pipe?
::乔纳森和科迪的哥哥乔希(如图所示)站在牛顿滑板公园半管道的顶端。 重力正在对滑板车施加下行力,正如照片所见。 为什么它不向边缘倾斜并开始向半管道的侧侧滚动呢?
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Inertia is the tendency of an object to resist a change in its motion. Because of inertia, a resting object will remain at rest, and a moving object will keep moving.
