Mars

Mars is the fourth planet from the Sun and the second smallest planet in the Solar System. Named after the Roman god of war, it is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the second highest known mountain within the Solar System (the tallest on a planet), and of Valleys Marineris, one of the largest canyons. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature.Mars has two known moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid.

Until the first successful Mars flyby in 1965 by Mariner 4, many speculated about the presence of liquid water on the planet's surface. This was based on observed periodic variations in light and dark patches, particularly in the polar latitudes, which appeared to be seas and continents; long, dark striations were interpreted by some as irrigation channels for liquid water. These straight line features were later explained as optical illusions, though geological evidence gathered by unmanned missions suggest that Mars once had large-scale water coverage on its surface. In 2005, radar data revealed the presence of large quantities of water ice at the poles and at mid-latitudes. The Mars rover Spirit sampled chemical compounds containing water molecules in March 2007. The Phoenix lander directly sampled water ice in shallow Martian soil on July 31, 2008.

Mars is currently host to five functioning spacecraft: three in orbit – the Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter; and two on the surface – Mars Exploration Rover Opportunity and the Mars Science Laboratory Curiosity. Defunct spacecraft on the surface include MER-A Spirit, and several other inert landers and rovers, both successful and unsuccessful, such as the Phoenix lander, which completed its mission in 2008. Observations by the Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.

Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches −3.0, which is surpassed only by Jupiter, Venus, the Moon, and the Sun. Optical ground-based telescopes are typically limited to resolving features about 300 km (186 miles) across when Earth and Mars are closest, because of Earth's atmosphere.

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Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System.Earth formed approximately 4.54 billion years ago, and life appeared on its surface within one billion years. Earth's biosphere then significantly altered the atmospheric and other basic physical conditions, which enabled the proliferation of organisms as well as the formation of the ozone layer, which together with Earth's magnetic field blocked harmful solar radiation, and permitted formerly ocean-confined life to move safely to land. The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist. Estimates on how much longer the planet will be able to continue to support life range from 500 million years , to as long as 2.3 billion years.

Earth's lithosphere is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods of many millions of years. About 71% of the surface is covered by salt water oceans, with the remainder consisting of continents and islands which together have many lakes and other sources of water that contribute to the hydrosphere. Earth's poles are mostly covered with ice that is the solid ice of the Antarctic ice sheet and the sea ice that is the polar ice packs. The planet's interior remains active, with a solid iron inner core, a liquid outer core that generates the magnetic field, and a thick layer of relatively solid mantle.

Earth gravitationally interacts with other objects in space, especially the Sun and the Moon. During one orbit around the Sun, the Earth rotates about its own axis 366.26 times, creating 365.26 solar days, or one sidereal year. The Earth's axis of rotation is tilted 23.4° away from the perpendicular of its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). The Moon is Earth's only natural satellite. It began orbiting the Earth about 4.53 billion years ago. The Moon's gravitational interaction with Earth stimulates ocean tides, stabilizes the axial tilt, and gradually slows the planet's rotation.

The planet is home to millions of species, including humans. Both the mineral resources of the planet and the products of the biosphere contribute resources that are used to support a global human population. These inhabitants are grouped into about 200 independent sovereign states, which interact through diplomacy, travel, trade, and military action. Human cultures have developed many views of the planet, including its personification as a planetary deity, its shape as flat, its position as the center of the universe, and in the modern Gaia Principle, as a single, self-regulating organism in its own right.

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Venus

Venus is the second planet from the Sun and the third smallest in our solar system . The planet is named after Venus , the Roman goddess of love, beauty and fertility. The Italian physicist Galileo Galileo observed the planet in the early 1600 s, and discovered that it had phases like the moon. This was among the first observations that clearly contradicted Ptolemy ' geocentric model that placed the earth at the center of the universe , and let the sun and the other planets revolve around the earth.

After the Moon , Venus is the brightest natural object in the night sky and it is bright enough to cast shadows. Since Venus is a planet in the present in relation to the earth, it seems never to be far away from the sun. If you are far enough north (for example, Tromse) on earth is Venus in certain periods circumpolar and visible all night. The same is the case in certain other periods if you are far enough south on earth. It is called the evening star when it is visible after sunset and morning star when it is visible before sunrise.

Venus is classified as a terrestrial planet and is sometimes called Earth's "sister planet" because of the relatively similar size, gravity and composition. The planet is covered by an opaque layer of highly reflective clouds of sulfuric acid to prevent the surface can be seen in visible light from space. Venus has the densest atmosphere of all the terrestrial planets in the solar system, consisting mostly of carbon dioxide . Venus has no carbon cycle that keeps carbon left in rocks and other surface features, and it does not appear that there are any organic life to absorb the carbon in biomass. The surface is a dusty dry desert landscape with many plate-like stones that are periodically refreshed by volcanism .

Early it was speculated much about the surface, but in the 1900 s revealed planetology some of the secrets, and in 1990-1991 charted Magellan project surface in detail. The reason is showing signs of extensive volcanism, and the sulfur in the atmosphere may indicate relatively recent eruptions. The lack of evidence of lava flows associated with the visible caldera remains an enigma. The planet has few impact craters , which shows that the surface is relatively young - ca. 300-600 million years old. There is no evidence of plate tectonics . This may be due to strong faults and that the mantle has a high viscosity . This difference between earth and Venus can be explained by the absence of water. Radioactivity create more heat in Venusian inner than that emitted at the surface.This heat may be released during periods when the surface is undergoing massive transformation.

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Kinetic Energy

A moving cricket ball can knock down the stumps. The cricket ball has energy because of its motion. When a stone is thrown with a great force, this fast moving stone can hit a window pane and break it. The stone has energy to do work on the window pane because of its motion. Thus, the energy possessed by a body due to its motion , is called Kinetic Energy.

                                                                                                                                            Kinetic Energy (K.E.) of a body having mass m, and velocity v, is equal to 1/2 mv 2.

                                                                  
                            i.e. K.E. = 1/2 mv 2

If  'm' is in kg, and 'v' is in m/s, then K.E. is in Joule (J).

1. Since the kinetic energy of a body is directly proportional to its mass, therefore, if the mass of a body is doubled, its kinetic energy also gets doubled and if the mass of body is halved, its kinetic energy also gets halved.
2. Since the kinetic energy of a body is directly proportional to the square of its velocity, therefore, if the velocity of a body is doubled, its kinetic energy becomes four times, and if the velocity of a body is halved, the kinetic energy becomes one-fourth.

Some examples of Kinetic Energy from our day to day life are:

1. The kinetic energy of running water is used to run the water mills.
2. The kinetic energy of the hammer is used to drive a nail in wood.
3. A bullet fired from a rifle can penetrate into a target because of its kinetic energy.

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