How does the human body move

Muscles move on commands from the brain. Single nerve cells in the spinal cord, called motor neurons, are the only way the brain connects to muscles. When a motor neuron inside the spinal cord fires, an impulse goes out from it to the muscles on a long, very thin extension of that single cell called an axon. When the impulse travels down the axon to the muscle, a chemical is released at its ending. Muscles are made of long fibers connected to each other longways by a ratchet mechanism, the kind of mechanism that allows the two parts of an extension ladder to slide past each other and then lock in a certain position. When the chemical impulse from the motor neuron hits the muscle, it causes to muscle fibers to rachet past each other, overlapping each other more, so that the muscle gets shorter and fatter. When the impulses from the nerves stop, the muscle fibers slide back to their original positions.

Each motor neuron connects to just one muscle, say the bicep on the front of your upper arm that lifts your forearm, or to the triceps, the one on the back that extends your forearm. But when you move, you never think, "I'd like to contract my bicep two inches and relax my tricep two inches" -- instead you think, "I'd like to put this cake in my mouth!" How does the brain translate from the general idea to lift something to your mouth to specific commands to muscles? It does it in stages. In the cerebral cortex, the commands in the neurons there represent coordinated movements - like pick up the cake, hit the ball, salute. The cortex then connects to a sort of console in the spinal cord that overlays the motor neurons. This console lays out arm position in space, up-down, left-right. Each desired arm position then is read out as a collection of specific commands to each motor neuron and muscle.(http://wiki.answers.com/Q/How_does_the_human_body_move)

Read more: http://wiki.answers.com/Q/How_does_the_human_body_move#ixzz1GRmRfcig

Stability and Balance

Stability and Balance
A concept closely related to the principles of equilibrium is stability. Stability is
defined mechanically as resistance to both linear and angular acceleration, or
resistance to disruption of equilibrium. An individual’s ability to control
equilibrium is known as balance. Different mechanical factors affect a body’s
stability. According to Newton’s second law of motion, the more massive an
object is, the greater is the force required to produce a given acceleration.
The greater the amount of friction is between an object and the surface or
surfaces it contacts, the greater is the force requirement for initiating or
maintaining motion. Another factor affecting stability is the size of the base of
support and CG.

Force

 Force and Momentum Concep


Understanding the concepts of inertia, mass, weight, pressure, volume,
density, specific weight, torque and impulse provides a useful foundation for
understanding the effects of forces.
(a) Concept and Definition
A force can be thought of as a push or pull acting on a body. Each force
is characterized by its magnitude, direction and point of application to a
given body. Body weight, friction, and air or water resistance are all
forces that commonly act on the human body. The action of force
causes a body’s mass to accelerate. Momentum, a mechanical quantity
that is particularly important in situations involving collisions. Momentum
may be defined generally as the quantity of motion  that an object
possesses. More specifically, linear momentum is the product of an
object’s mass and its velocity. A static object (with zero velocity) has no
momentum; that is, its momentum equals zero. A change in a body’s
momentum may be caused by either a change in the body’s mass or a
change in its velocity.

(b) Application of Force and Momentum
Units of force are units of mass multiplied by units of acceleration. In the
metric system, the most common unit of force is the Newton(N), which
is the amount of force required to accelerate 1 kg  of mass at 1 m/s2
Because a number of forces act simultaneously in most situations,
constructing a free body diagram is usually the first step when analyzing
the effects of forces on a body or system of interest. A free body is any
object, body, or body part that is being focused upon for analysis. When
all acting forces are balanced, or cancel each other out, the net force is
zero, and the body remains in its original state of motion, either
motionless or moving with a constant velocity. When a net force is
present, the body moves in the direction of the net force and with an
acceleration that is proportional to the magnitude of the net force. Units
of momentum are units of mass multiplied by units of velocity,
expressed in terms of kg m/s. Because velocity is a vector quantity,

momentum is also a vector quantity and is subject to the rules of vector
composition and resolution. When a head-on collision between two
objects occurs, there is a tendency for both objects to continue moving
in the direction of motion originally possessed by  the object with the
greatest momentum.

Centripetal and Centrifugal Forces
Bodies undergoing rotary motion around a fixed axis are also subject to a
linear force. When an object attached to a line is whirled around in a circular
path and then released, the object flies off on a path that forms a tangent to
the circular path it was following at the point at which it was released, since
this is the direction it was travelling in at the point of release. Centripetal force
prevents the rotating body from leaving its circular path while rotation occurs
around a fixed axis. The direction of a centripetal force is always toward the
centre of rotation; this is the reason it is also known as centre seeking force.
Centripetal force produces the radial component of the acceleration of a body
travelling on a curved path. The magnitude of centripetal force depends on
the mass, speed, and radius of rotation of the rotating body. When rounding a
corner in a relay race, there is a sensation of being pushed in the direction of
the outside of the curve. What is felt has been referred to as centrifugal force.
This is because, according to Newton’s first law, the body’s inertia tends to
cause it to continue travelling on a straight, rather than a curved path.



Readings
Susan J. Hall. (1999). Basic biomechanics.(5th ed.). Boston: WCB/McGrawHill

NEWTON

Hukum Newton memainkan peranan yang penting dalam kehidupan manusia. Boleh dikatakan setiap pergerakan manusia melibatkan hukum-hukum tersebut. Hukum Newton Pertama menyatakan bahawa sesuatu objek akan kekal dalam keadaan pegun atau terus bergerak dengan halaju seragam dalam satu garisan lurus sehinggalah ada suatu daya luar bertindak terhadapnya.

            Hukum Newton Kedua pula menyatakan perubahan terhadap gerakan adalah berkadar terus dengan daya yang dikenakan dan dalam arah garisan lurus di mana arah daya itu dikenakan. Jadi, jelaslah bahawa Hukum Newton Pertama berkaitan dengan hukum Newton Kedua.

            Hukum Newton Ketiga pula menyatakan bahawa setiap tindakan (aksi) sesuatu objek akan terdapat satu tindakbalas (reaksi) yang sama magnitud tetapi dalam arah yang bertentangan. Hukum ini juga digunakan dalam teknologi angkasa lepas untuk melancarkan roket. Begitu juga dengan kapal terbang yang mengenakan aksi pada sayap manakala angin pula memberi reaksi bertentangan kepada kapal terbang untuk terbang tinggi.

Instrumentasi

Definisi Terminalogi: Instrumentasi (instrumentation)
Merupakan sejenis alat (tool) yang digunakan untuk mengukur dan mendapatkan data secara saintifik dan sistematik. Data yang dikumpulkan berbentuk kuantitatif dan kualitatif. Data yang diperolehi oleh pengkaji digunakan untuk dianalisis bagi menjawab persoalan kajian yang telah ditetapkan. Ahmad Hashim ( 2004) menyatakan instrumen merupakan alat ujian yang digunakan untuk mengukur dan menilai maklumat. Insrtumen yang digunakan mestilah mempunyai komponen kebolehpercayaan, objektiviti dan kesahan. Penggunaan instrumen yang piawai secara berterusan dapat meningkatkan kualiti pengajaran dan pembelajaran. Jika instrumen yang digunakan tidak mempunyai kesahan, kebolehpercayaan dan keobjektifan yang lemah ia akan memberi dapatan dan keputusan ujian yang boleh dipertikaikan. Mengikut Johnson dan Nelson (1986) secara umumnya terdapat 4 aspek penting dalam pemilihan dan pembinaan instrumen iaitu:
i. Kesahan
ii. Kebolehpercayaan
iii. Objektif
iv. Norma
Next Posts :Ujian Makmal (Laboratory Testing),Ujian Lapangan (field Testing),Bateri Ujian (Test Battery),Pemerhatian Sistematik (Systematic Obsservation),Instrumen Untuk Tinjauan (survey Instruments) @ dapatkan nota penuh secara percuma di

http://www.ziddu.com/download/5416763/asignmnt_1.doc.html

Fasa Pegangan Peluru

Fasa Pegangan Peluru (Grip):

Cara memegang peluru boleh dibahagikan kepada dua.
Cara memegang dengan lima jari. Kelima-lima jari digunakan untuk memegang peluru.
Cara memegang dengan tiga jari. Peluru disokong oleh tiga jari tangan tengah. Ibu jari dan jari kelengkeng menyangga peluru.
Fasa Lakuan Sedia (Preparation)


Lungsuran (Glide)



Lontaran (Delivery Phase)

Dalam fasa lontaran yang pertama ini ianya membantu mengekal kelajuan lontaran dan menyediakan posisi untuk lontaran.

Dalam fasa lontaran kedua ini pula objektif utamanya ialah untuk memindahkan daya kelajuan yang dihasilkan oleh pelontar ke sasaran.

Dalam fasa ini objektif yang sama seperti di bahagian dua di mana dalam fasa ini pelontar melengkapkan pergerakan tangan hingga selesai

Pulihan (Recovery)
Dalam fasa ini tujuan utama pergerakan akhir pelontar ialah untuk menstabilkan posisi dirian setelah lontaran dibuat. Fasa pulihan ini juga membantu mengelak pelontar dari terbatal.

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