Law of motion

Newton's First Law of Motion

Every object remains in a state of rest or of uniform motion in a straight line unless acted upon by an outside force." (An outside force is a net force.) ¬An object at rest will stay at rest, forever, as long as nothing pushes or pulls on it. An object in motion will stay in motion, traveling in a straight line, forever, until something pushes or pulls on it.

inertia

It is that property of matter which opposes changes in velocity. Inertia is the resistance to changes in motion. Inertia is proportional to mass. Big masses resist changing their motion more than smaller masses.

Newton's Second Law of Motion

Newton's Second Law of Motion defines the relationship between acceleration, force, and mass. force and acceleration are directly proportional, while mass and acceleration are inversely proportional. ¬When a force acts on an object, the object accelerates in the direction of the force. If the mass of an object is held constant, increasing force will increase acceleration. If the force on an object remains constant, increasing mass will decrease acceleration.

Newton's Third Law

When one object exerts a force on a second object, the second object also exerts a force on the first object. The two forces are equal in strength and oriented in opposite directions. The third law states that for every force there is an equal and opposite force. For example, if you push on a wall, it will push back on you as hard as you are pushing on it.

Mars Explore

Viking 1 & 2

Orbiters

Launch: August 20, 1975 (Viking 1); September 9, 1975 (Viking 2)

Arrival: June 19, 1976 (Viking 1); August 7, 1976 (Viking 2)

Landers

Landing: July 20, 1976 (Viking 1); September 3, 1976 (Viking 2)

Mass: 576 kilograms (1,270 pounds)

Science instruments: Biology instrument, gas chromatograph/mass spectrometer, X-ray fluorescence spectrometer, seismometer, meteorology instrument, stereo color cameras, physical and magnetic properties of soil, aerodynamic properties and composition of Martian atmosphere with changes in altitude

Overview

NASA's Viking Project found a place in history when it became the first U.S. mission to land a spacecraft safely on the surface of Mars and return images of the surface. Two identical spacecraft, each consisting of a lander and an orbiter, were built. Each orbiter-lander pair flew together and entered Mars orbit; the landers then separated and descended to the planet's surface.

The Viking 1 lander touched down on the western slope of Chryse Planitia (the Plains of Gold), while the Viking 2 lander settled down at Utopia Planitia.

Besides taking photographs and collecting other science data on the Martian surface, the two landers conducted three biology experiments designed to look for possible signs of life. These experiments discovered unexpected and enigmatic chemical activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms in soil near the landing sites. According to scientists, Mars is self-sterilizing. They believe the combination of solar ultraviolet radiation that saturates the surface, the extreme dryness of the soil and the oxidizing nature of the soil chemistry prevent the formation of living organisms in the Martian soil.

The Viking mission was planned to continue for 90 days after landing. Each orbiter and lander operated far beyond its design lifetime. Viking Orbiter 1 continued for four years and 1,489 orbits of Mars, concluding its mission August 7, 1980, while Viking Orbiter 2 functioned until July 25, 1978. Because of the variations in available sunlight, both landers were powered by radioisotope thermoelectric generators -- devices that create electricity from heat given off by the natural decay of plutonium. That power source allowed long-term science investigations that otherwise would not have been possible. Viking Lander 1 made its final transmission to Earth November 11, 1982. The last data from Viking Lander 2 arrived at Earth on April 11, 1980.

Gravitational field intensity

Gravitational field intensity (gravitational field strength) is the amount of force applied on each unit of mass of an object at a point in space. "Space" includes a region on or near the surface of a planet.

This means that the gravitational field strength, g is equal to the force experienced by a mass of 1kg in that gravitational field.

acceleration due to gravity

The acceleration due to gravity is the acceleration of a body due to the influence of the pull of gravity alone, usually denoted by 'g'. This value varies from one celestial body to another. For example, the acceleration due to gravity would be different on the Moon as compared to the one here on Earth. Similarly, you would have different values for both Jupiter and Pluto.

Galileo theorized that in the absence of air, all things would truly fall with the same acceleration. 300 years later the crew of Apollo-15 demonstrated this on the Moon (which has gravity but lacks air) by dropping a hammer and a feather.

An atomic watch is handy because it automatically adjusts for Daylight Saving Time (DST), often mispronounced as Daylight Savings Time, leap years and even leap seconds. It contains an internal antenna and program that is set to search once a day for the 60 kHz radio signal emitted from the WWVB transmitter in Ft. Collins. When it finds the signal it decodes the time then sets itself. The Ft. Collins transmitter has a radius of 1,864 miles (3,000 km), making it available to the most of the United States with the exception of Hawaii and Alaska.

If you travel overseas with an atomic watch, it will continue to function as a quartz watch but will not receive radio controlled updates. Although Europe has its own atomic clocks, the transmitter frequency used in Europe differs from the one used in the United States.

(WWVB is a NIST time signal radio station near Fort Collins, Colorado, co-located with WWV. WWVB is the station that radio-controlled clocks throughout North America use to synchronize themselves.)

Electric watch, which commonly means any watch that is powered by electricity, in horology has become a generic term for the first generation of electrically powered watches which appeared starting in 1957, before the invention of quartz watches in the 1970s. Their timekeeping element was either a traditional balance wheel or a tuning fork, driven electromagnetically by a solenoid powered by a battery

Gravitation

Newton defined gravity as a force -- one that attracts all objects to all other objects. It causes any two objects in the universe to be drawn to one another. Gravity assisted in forming the universe, that it keeps the moon in orbit around the Earth.

Gravitation

Gravitation is the force of attraction that acts between all objects because of their mass. An object's mass is its amount of matter. Because of gravitation, an object that is near Earth falls toward the surface of the planet. An object that is already on the surface experiences a downward force due to gravitation. We experience this force on our bodies as our weight. Gravitation holds together the hot gases that make up the sun, and it keeps the planets in their orbits around the sun. Another term for gravitation is the force of gravity.

People misunderstood gravitation for centuries. In the 300's B.C., the Greek philosopher and scientist Aristotle taught the incorrect idea that heavy objects fall faster than light objects. People accepted that idea until the early 1600's, when the Italian scientist Galileo corrected it. Galileo said that all objects fall with the same acceleration unless air resistance or some other force acts on them. An object's acceleration is the rate of change of its velocity (speed in a particular direction). Thus, a heavy object and a light object that are dropped from the same height will reach the ground at the same time

Black holes

Einstein's theory predicts the existence of objects called black holes. A black hole is a region of space whose gravitational force is so strong that not even light can escape from it. Researchers have found strong evidence that most very massive stars eventually evolve into black holes, and that most large galaxies have a gigantic black hole at their centers.

Mathematical Principles of Natural Philosophy published - 1687

in 1665 newton was 23 years old

Introduction to Free Fall

A free-falling object is an object which is falling under the sole influence of gravity. Any object which is being acted upon only be the force of gravity is said to be in a state of free fall. There are two important motion characteristics which are true of free-falling objects:

• Free-falling objects do not encounter air resistance.

• All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s (often approximated as 10 m/s/s for back-of-the-envelope calculations)

Virus

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Most viruses are too small to be seen directly with a light microscope. Viruses infect all types of organisms, from animals and plants to bacteria and archaea. Since the initial discovery of tobacco mosaic virus by Martinus Beijerinck in 1898, about 5,000 viruses have been described in detail, although there are millions of different types. Viruses are found in almost every ecosystem on Earth and are the most abundant type of biological entity.The study of viruses is known as virology, a sub-speciality of microbiology.

Virus particles (known as virions) consist of two or three parts: genes made from either DNA or RNA, long molecules that carry genetic information; a protein coat that protects these genes; and in some cases an envelope of lipids that surrounds the protein coat when they are outside a cell. The shapes of viruses range from simple helical and icosahedral forms to more complex structures. The average virus is about one one-hundredth the size of the average bacterium.

properties

Opinions differ on whether viruses are a form of life, or organic structures that interact with living organisms. They have been described as "organisms at the edge of life", since they resemble organisms in that they possess genes and evolve by natural selection, and reproduce by creating multiple copies of themselves through self-assembly. Although they have genes, they do not have a cellular structure, which is often seen as the basic unit of life. Viruses do not have their own metabolism, and require a host cell to make new products. They therefore cannot naturally reproduce outside a host cell—although bacterial species such as rickettsia and chlamydia are considered living organisms despite the same limitation.

Replication cycle

Viral populations do not grow through cell division, because they are acellular; instead, they use the machinery and metabolism of a host cell to produce multiple copies of themselves, and they assemble in the cell.

Virus Transmission in detail

Virus transmission can be defined as the movement of pathogens from one host to another. The transmission can occur within the same species or between different species too. Transmission of virus is the main way in which diseases are spread. In infectious diseases, the spread of the virus can be controlled by ensuring that the transmission does not occur.

sexual reproduction

sexual reproduction is the process of fertilization, whereby the male and female sex cells fuse, or bond. Fertilization may be of two types, either internal or external. Animals typically produce male gametes called sperm, and female gametes called eggs and ova, following immediately after meiosis.

Sexual reproduction is a complex process involving two individuals or parents of different sexes i.e. male and female. The formation of two different types of gametes by male and female takes place in their gonads i.e., testis in male and ovary in female. The sperms are produced in the testis and ova are produced by ovary. Therefore testes and ovaries are called primary sex organs. The spermatozoa are formed in the testis by the process of spermatogenesis and ova in the ovary by the process of oogenesis. The spermatogenesis and oogenesis are altogether known as gametogenesis. The formation of gametes by gonads is the primary sex character of male and female. In association with this, secondary sex characters also develop in sexually reproducing animals.

Flowering plants

The anther produces male gametophytes, the sperm is produced in pollen grains, which attach to the stigma on top of a carpel, in which the female gametophytes (inside ovules) are located. After the pollen tube grows through the carpel's style, the sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed double fertilization. The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female cells) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced the female gametophyte(s), then grows into a fruit, which surrounds the seed(s). Plants may either self-pollinate or cross-pollinate. Nonflowering plants like ferns, moss and liverworts use other means of sexual reproduction.

sporulation

sporulation

Spores are usually haploid and unicellular and are produced by meiosis in the sporangium by the sporophyte. Once conditions are favorable, the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, which eventually goes on to produce gametes.

vegetative propagation, the ability of plants to reproduce without sexual reproduction, by producing new plants from existing vegetative structures. Some plants, such as the Canada thistle and most bamboos, send out long underground stems that produce new plants, often at considerable distances from the original plant. Such plants can form enormous colonies of new plants within a relatively few years.

Vegetative reproduction is a type of asexual reproduction for plants, and is also called vegetative propagation, vegetative multiplication, or vegetative cloning. It is a process by which new plant "individuals" arise or are obtained without production of seeds or spores. It is both a natural process in many plant species (as well as non-plant organisms such as bacteria and fungi) and one used or encouraged by horticulturists to obtain quantities of economically valuable plants. A related technique used in cultivation is tissue culture, which involves vegetative reproduction under sterile conditions.

Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings

Grafting is a method of asexual plant propagation widely used in agriculture and horticulture where the tissues of one plant are encouraged to fuse with those of another. It is most commonly used for the propagation of trees and shrubs grown commercially.

bryophyllum

from the Greek bryo (sprout) and phyllon (leaf)

Regeneration: A form of asexual reproduction that take place in some invertebrates from the animal kingdom. These also produce offspring that are identical to parent. Planaria, a type of flat worm, reproduces itself by dividing in two and regenerating the missing parts. They also have the ability to regenerate injured body parts.

U.S. medical scientists have determined the way the human liver renews itself might be a simpler process than had been assumed. Harvard Medical School researchers said their findings could significantly affect the way physicians make livers regrow in patients who have liver diseases such as cirrhosis, hepatitis or cancer.

Reproduction

Reproduction is the biological process by which new "offspring" individual organisms are produced from their "parents". Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: sexual and asexual.

In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a bacterial cell into two daughter cells is an example of asexual reproduction. Asexual reproduction is not, however, limited to single-celled organisms. Most plants have the ability to reproduce asexually.

Sexual reproduction typically requires the involvement of two individuals or gamates, one each from opposite type of sex.

Asexual reproduction

Asexual reproduction is the process by which an organism creates a genetically-similar or identical copy of itself without a contribution of genetic material from another individual. Bacteria divide asexually via binary fission; viruses take control of host cells to produce more viruses; Hydras (invertebrates of the order Hydroidea) and yeasts are able to reproduce by budding. These organisms often do not possess different sexes, and they are capable of "splitting" themselves into two or more individuals. On the other hand, some of these species that are capable of reproducing asexually, like hydra, yeast (See Mating of yeasts] and jellyfish, may also reproduce sexually. For instance, most plants are capable of vegetative reproduction—reproduction without seeds or spores—but can also reproduce sexually. Likewise, bacteria may exchange genetic information by conjugation. Other ways of asexual reproduction include parthenogenesis, fragmentation and spore formation that involves only mitosis. Parthenogenesis (from the Greek παρθένος parthenos, "virgin", + γένεσις genesis, "creation") is the growth and development of embryo or seed without fertilization by a male. Parthenogenesis occurs naturally in some species, including lower plants (where it is called apomixis), invertebrates (e.g. water fleas, aphids, some bees and parasitic wasps), and vertebrates (e.g. some reptiles fish, and, very rarely, birds and sharks]). It is sometimes also used to describe reproduction modes in hermaphroditic species which can self-fertilize.

Binary Fission

Binary fission involves mitosis only and hence the resultant individuals are genetically identical to each other and to the parent.

Binary Fission in Amoeba

It is the simplest and most common method of asexual reproduction. The whole parental body acts as the reproductive unit. The nucleus of the unicellular parent organism divides into two. This is followed by the division of the cytoplasm and 2 daughter cells of almost equal size are formed. The daughter cells grow in size and then divide again.

Examples: Seen in euglena, amoeba, paramoecium.

Based on the plane of cytoplasmic division binary fission is of 3 types, namely:

a) Simple binary fission

b) Transverse binary fission

c) Longitudinal binary fission

Multiple Fission

In some organisms the nucleus of the parent divides into many daughter nuclei by repeated divisions (amitosis). This is followed by the division of the cytoplasm into several parts with each part enclosing one nucleus. So a number of daughter cells are formed from a single parent at the same time. This kind of fission is known as multiple fission.

A - C Cyst Formation and Multiple Fission in AmoebaD - F Multiple Fission in Malarial Parasite

Example: Seen in Plasmodium (malarial parasite) where it is known as schizogony or sporulation, amoeba.

During unfavourable conditions, amoeba withdraws its pseudopodia, becomes almost round and secretes a three-layered hard covering called cyst around itself. This phenomenon is called encystation and lasts till the favourable conditions set in. On the onset of favourable conditions, the encysted amoeba divides by multiple fission to produce a large number of minute pseudopodiospores. At this point, the cyst bursts open and the spores are liberated into the surrounding medium. Each pseudopodiospore develops into an amoeba. This entire process is termed as sporulation

Budding

Here one or more outgrowths of reproductive units called buds are formed on the parental body. Each bud consists of a small group of cells surrounded by the epithelium.

A bud develops as a small outgrowth on the parents body. Each bud enlarges, develops the characteristics of the parent organism. A bud may become separated from the parent body and then develop into a new individual, or it may separate only after the completion of development. In some cases the buds never separate and as a result, colonies of interconnected individuals are formed.

Examples: Hydra, sponges, some tunicates.

Internal buds

In case of sponges, the parent releases a specialised mass of cells enclosed in a common opaque envelope, called as the gemmule. Gemmules are thought to be internal buds, which on germination give rise to an offspring.

Budding in Hydra and Sponge