length

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length

1. Prosody Phonetics the metrical quantity or temporal duration of a vowel or syllable
2. the distance from one end of a rectangular swimming bath to the other
3. Prosody the quality of a vowel, whether stressed or unstressed, that distinguishes it from another vowel of similar articulatory characteristics. Thus in English beat is of greater length than in English bit
4. Cricket the distance from the batsman at which the ball pitches
5. Bridge a holding of four or more cards in a suit

Length

A one-dimensional extension in space. Length is one of the three fundamental physical quantities, the others being mass and time. It can be measured by comparison with an arbitrary standard; the specific one in most common usage is the international meter. In 1983, at the meeting of the Conférence Général des Poids et Mésures, the meter was redefined in terms of time and the speed of light: “The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.” This definition defines the speed of light to be exactly 299 792 458 m/s, and defines the meter in terms of the most accurately known quantity, the second. See Light, Mass, Time

Length

 

a numerical characteristic of the extent of curves. The concept of length is defined differently for different cases. (1) The length of a line segment is the distance between its end points, measured by some segment taken as a unit of length. (2) The length of a polygonal line is the sum of the lengths of its components. (3) The length of a simple arc is the limit of the lengths of polygonal lines inscribed in the arc, when the number of components increases indefinitely and the maximum length of the components tends to zero. (4) The length of a continuous curve consisting of a finite number of simple arcs is equal to the sum of the lengths of these arcs. For example, the circumference of a circle can be obtained as the limit of the perimeters of inscribed regular polygons when the number of their sides is doubled indefinitely; it is equal to 2πR where R is the radius of the circle. Any continuous curve has finite or infinite length. If its length is finite, then the curve is said to be rectifiable. The graph (see Figure 1) of the function

for 0 <x ≤ 1 and f(x) = 0 when x = 0 is an example of a nonrectifiable curve; here the lengths of the inscribed polygonal lines increase beyond all bound as the length of the components tend to zero. If the equation of a plane curve has the form y =f(x) (a ^ x ^ b)m rectangular coordinates and the function f(x) has a continuous derivative f’(x), then the length of the curve is given by the integral

The length of a curve given in parametric form and the length of a space curve can be expressed in a similar manner.

Figure 1

To calculate the length of a curve the mathematicians of antiquity essentially used lengths of polygonal lines and passage to the limit. For them, however, such passage to the limit was only a method for calculating the length of a curve and not for defining the concept of the length of a curve, since they apparently perceived the latter as one of the elementary mathematical concepts. The necessity of defining the length of a curve became clear only in the first half of the 19th century. A full elucidation of the problem was achieved by C. Jordan. In differential geometry the length of a curve is also defined on a surface or in an arbitrary Riemannian space.

REFERENCES

Lebesgue, H. Ob izmerenii velichin, 2nd ed. Moscow, 1960. (Translated from French.)
Fikhtengol’ts, G. M. Kurs differentsial’nogo i integral’nogo ischisleniya, 7th ed. vol. 2. Moscow, 1969.

length

[leŋkth]
(mechanics)
Extension in space.
References in periodicals archive ?
Improvements were also observed in neural mobility and muscle length (hamstrings and iliopsoas).
Isotonic exercise movements act to change muscle length with muscle tension remaining relatively constant.
25-27) Furthermore, medializing the humerus also moves the rotator cuff insertions, which shortens the residual rotator cuff muscle length and can have negative implications on postoperative internal and external rotation.
We then found the necessary muscle excitations, such that the product of muscle force generated at the current muscle length and the current muscle moment arm equaled the required active torque for the unconstrained joints, if feasible.
These tests are arranged into groups such as anthropometric assessment, muscle length assessment and speed, agility and quickness testing so that therapists and clinicians can choose the correct procedure in less time.
Variations in adductor muscle length and weight could also be indicative of energy allocation related to reproductive events (Dore 1991).
Dynamic exercise is characterized by a change in muscle length against a small load.
The application of the same torque at each measurement session ensures that any change in passive range of motion measured is due to a change in muscle length and stiffness rather than to a change in the applied torque or to a change in the individual's tolerance to stretch.
Doctors at University Hospital, Walsgrave, who treat Mr O'Neill, say tilt tables help to maintain blood pressure, bone strength and muscle length.
One week following the injury, gentle flexibility exercises were added to improve hip and knee ROM as well as hamstring, hip flexor and calf muscle length.
The section of "Treatment Approaches" includes chapters on manual therapy and myofascial (soft tissue) techniques, muscle length and strength testing, and rehabilitative exercises.
The progressive stimulation of the musculature with strength-training movements reduces neural inhibitory impulses -- the impulses that are picked up by the sensory receptors that monitor changes in muscle length and serve as protective mechanisms.