Making the Leap
Jumps play a big role in many styles of dancing. Generally, what makes a jump impressive is its hang time, the amount of time a dancer spends in the air.
The quest for greater hang time is a battle against gravity, the constant downward pull of Earth, said Laws. To leave the ground at all, a dancer has to use leg muscles to create an upward push that is greater than Earth’s downward pull. But the final height of any depends on just one thing; the upward speed of the body just as the dancer leaves the ground.
Strengthening muscles so they can push harder is one obvious way to achieve higher jumps and increase hang time. But ballet dancers also use a simple trick to gain the illusion of staying in the air longer without actually doing so.
In a huge sideways jumps called a grand jete, a skillful ballet dancer seems to float fro an impossible length of time. Of course, a dancer can’t really hang in the air. The laws of physics decree that during any jump, a dancer’s center of gravity must follow a parabola. A parabola is the same curved path a ball takes when you throw it into the air. So do dancers make it look like they’re hanging in the air?
A dancer creates the illusion of floating in the air by lifting her legs and arms as she approaches the peak of the jump. The rest of her body-her torso and her head-respond by sinking a bit. If her timing is just right, she’ll seem to float sideways, instead of rising and falling. The effect is not only beautiful; it also makes the jump seem bigger by "stretching out" the peak.
Of course, what goes up must come down. During a typical grand jete, a dancer’s center of gravity rises 2 feet off the ground. Pulled by gravity from such a height, the dancer’s body falls very fast-roughly 3.4 meters per second-by the time it reaches the floor. As it falls, body carries with it momentum. Momentum is the weight of the body multiplied by its speed. The bigger the body is and the faster it falls, the greater its momentum.
The only way a dancer can stop dropping through the air is by stopping the body’s momentum, which requires an opposing force-the ground. Landing can be very jarring to a dancer and can cause injuries. The dancer can ease the landing by needing her knees and letting her arms fall, but she also gets help from an unexpected source: the floor. Wooden dance floors are designed to act like shock absorbers. They are springy and can recoil as mush as an 9ch under extreme pressure. That little bit of give makes a big difference. Landing on a springy floor, the dancer undergoes a slower change in momentum than she would hitting a rigid floor. The give in the floor allows the decrease in momentum to happen more gradually with less force and less chance of injury. [理工类A]
纵身一跃
在许多不同风格的舞蹈表演中，跳跃都是很关键的一项。一般说来，让一个跳跃动作精彩的因素不在于它的停留时间，即舞者在空中停留的时间。
追求更长的空中停留时间实际上是和重力的一场较量，重力是地球对你往下拉的力量，要整个身子都脱离地面。舞者必须用腿部肌肉的力量创造出一个比重力更的向上的冲力。但是最后最高的高度只取决于一件事，即舞者脱离地面向上跳时的速度小。
一种用来达到跳得更高，空中停留时间更长的很明显的做法是通过加强肌肉以使它能更有强度地推动身体往上跳。但是芭蕾舞蹈演员也用一种小小的又很简单的技巧来制造一种停留空中很长时间的假象，但实际上他们并没停留多长时间。
在一种幅度的侧身跳跃动作（小跳）中，一个技艺精湛的芭蕾舞演员好像在空中可以停上一段让人难以置信的时间。当然，一个舞者不可能真正地在空中悬着的。物理学中的定理规定了在任何一种跳跃中，一个舞者的重心是循着一条抛物线的轨迹走的。一条抛物线就如同一个你随手扔去的球所经过的路线。但是一个舞者如何做到使他们看起来像是在空中悬着的呢？
一个舞者在她达到跳跃过程中最高处时伸展她的双腿和双臂，从而创造了一个停在空中的幻觉。她身体的其他部分如躯干和头部则相应地下沉一点。如果时间控制得好，她就会看起来像是侧面浮在空中，而不是上升或下降，所产生的效果则不仅仅是漂亮的动作，而且也使这跳跃看起来更，因为它在跳得最高的时候“伸展”开了。
当然，不可否认的是，跳上去就必定得落下来。在一个标准的芭蕾舞小跳动作中，舞者的重心跃到离地2英尺的高处。在这样的高度受重力拉动，她的身体将以每秒约3.4米的速度往下坠。在下落的过程当中，身体是带有动量的。一个人的动量的小是体重和速度的乘积值表示的。体重越，下落的速度越快，动量就越。
舞者要阻止从空中掉落的惟一方法便是中止自己的动量，而这需要一个反面的来自一个平面的阻力。对舞蹈演员来说，落地会产生很的反弹力，也有可能因此受伤。舞蹈演员可能以通过屈膝和放下手臂来对落地来一下缓冲，但她同时也可以得到地面这意想不到的帮助。木制的舞蹈地板被设计成像是震动吸收者。它们有弹性，可以后缩，在非常的压力之下可以后缩到一英寸。这么一个小小的弹性产生的作用可不小。舞蹈演员如果落在有弹性的地板上将使动量变化过程比落在一块硬地上的要慢。这个弹力使动量减少的过程更为缓慢，因而只带有较少的冲击力和受伤的几率。
Jumps play a big role in many styles of dancing. Generally, what makes a jump impressive is its hang time, the amount of time a dancer spends in the air.
The quest for greater hang time is a battle against gravity, the constant downward pull of Earth, said Laws. To leave the ground at all, a dancer has to use leg muscles to create an upward push that is greater than Earth’s downward pull. But the final height of any depends on just one thing; the upward speed of the body just as the dancer leaves the ground.
Strengthening muscles so they can push harder is one obvious way to achieve higher jumps and increase hang time. But ballet dancers also use a simple trick to gain the illusion of staying in the air longer without actually doing so.
In a huge sideways jumps called a grand jete, a skillful ballet dancer seems to float fro an impossible length of time. Of course, a dancer can’t really hang in the air. The laws of physics decree that during any jump, a dancer’s center of gravity must follow a parabola. A parabola is the same curved path a ball takes when you throw it into the air. So do dancers make it look like they’re hanging in the air?
A dancer creates the illusion of floating in the air by lifting her legs and arms as she approaches the peak of the jump. The rest of her body-her torso and her head-respond by sinking a bit. If her timing is just right, she’ll seem to float sideways, instead of rising and falling. The effect is not only beautiful; it also makes the jump seem bigger by "stretching out" the peak.
Of course, what goes up must come down. During a typical grand jete, a dancer’s center of gravity rises 2 feet off the ground. Pulled by gravity from such a height, the dancer’s body falls very fast-roughly 3.4 meters per second-by the time it reaches the floor. As it falls, body carries with it momentum. Momentum is the weight of the body multiplied by its speed. The bigger the body is and the faster it falls, the greater its momentum.
The only way a dancer can stop dropping through the air is by stopping the body’s momentum, which requires an opposing force-the ground. Landing can be very jarring to a dancer and can cause injuries. The dancer can ease the landing by needing her knees and letting her arms fall, but she also gets help from an unexpected source: the floor. Wooden dance floors are designed to act like shock absorbers. They are springy and can recoil as mush as an 9ch under extreme pressure. That little bit of give makes a big difference. Landing on a springy floor, the dancer undergoes a slower change in momentum than she would hitting a rigid floor. The give in the floor allows the decrease in momentum to happen more gradually with less force and less chance of injury. [理工类A]
纵身一跃
在许多不同风格的舞蹈表演中，跳跃都是很关键的一项。一般说来，让一个跳跃动作精彩的因素不在于它的停留时间，即舞者在空中停留的时间。
追求更长的空中停留时间实际上是和重力的一场较量，重力是地球对你往下拉的力量，要整个身子都脱离地面。舞者必须用腿部肌肉的力量创造出一个比重力更的向上的冲力。但是最后最高的高度只取决于一件事，即舞者脱离地面向上跳时的速度小。
一种用来达到跳得更高，空中停留时间更长的很明显的做法是通过加强肌肉以使它能更有强度地推动身体往上跳。但是芭蕾舞蹈演员也用一种小小的又很简单的技巧来制造一种停留空中很长时间的假象，但实际上他们并没停留多长时间。
在一种幅度的侧身跳跃动作（小跳）中，一个技艺精湛的芭蕾舞演员好像在空中可以停上一段让人难以置信的时间。当然，一个舞者不可能真正地在空中悬着的。物理学中的定理规定了在任何一种跳跃中，一个舞者的重心是循着一条抛物线的轨迹走的。一条抛物线就如同一个你随手扔去的球所经过的路线。但是一个舞者如何做到使他们看起来像是在空中悬着的呢？
一个舞者在她达到跳跃过程中最高处时伸展她的双腿和双臂，从而创造了一个停在空中的幻觉。她身体的其他部分如躯干和头部则相应地下沉一点。如果时间控制得好，她就会看起来像是侧面浮在空中，而不是上升或下降，所产生的效果则不仅仅是漂亮的动作，而且也使这跳跃看起来更，因为它在跳得最高的时候“伸展”开了。
当然，不可否认的是，跳上去就必定得落下来。在一个标准的芭蕾舞小跳动作中，舞者的重心跃到离地2英尺的高处。在这样的高度受重力拉动，她的身体将以每秒约3.4米的速度往下坠。在下落的过程当中，身体是带有动量的。一个人的动量的小是体重和速度的乘积值表示的。体重越，下落的速度越快，动量就越。
舞者要阻止从空中掉落的惟一方法便是中止自己的动量，而这需要一个反面的来自一个平面的阻力。对舞蹈演员来说，落地会产生很的反弹力，也有可能因此受伤。舞蹈演员可能以通过屈膝和放下手臂来对落地来一下缓冲，但她同时也可以得到地面这意想不到的帮助。木制的舞蹈地板被设计成像是震动吸收者。它们有弹性，可以后缩，在非常的压力之下可以后缩到一英寸。这么一个小小的弹性产生的作用可不小。舞蹈演员如果落在有弹性的地板上将使动量变化过程比落在一块硬地上的要慢。这个弹力使动量减少的过程更为缓慢，因而只带有较少的冲击力和受伤的几率。
