General Science GK Questions with Answers – Page 64

This is absolute zero, more exactly −273.15°C or 0 kelvin, the temperature below which nothing can be cooled. Temperature measures the random motion of particles.

One hertz means one complete cycle per second, so a frequency of 3 Hz means the current completes three full cycles every second.

Pitch is how the ear perceives the frequency of a sound, so a higher pitch means more vibrations per second.

Streptococcus mutans turns dietary sugar, especially sucrose, into a sticky slime that glues it to the teeth. The bacterium makes enzymes called glucosyltransferases that join the glucose units of sucrose into sticky chains called glucans.

These three oxides, made by heating limestone with clay, form the compounds that make cement set and harden. Portland cement was patented by Joseph Aspdin in England in 1824, and named after Portland stone, which the set cement resembled.

The weight we feel is really the push of the floor on us, and in orbit that push disappears. The space station and the astronaut are both in free fall around the Earth.

A thermocouple has no liquid that can freeze, so suitable types can read temperatures far below −200°C. A thermocouple is made of two wires of different metals joined at a junction.

Kepler's third law says the square of a planet's orbital period is proportional to the cube of the semimajor axis of its orbit.

A convex lens forms an image at the same distance as the object only when the object sits at 2f, and here 2f works out to 4R/3.

Subrahmanyan Chandrasekhar showed that a white dwarf, which is supported against gravity by the pressure of degenerate electrons, cannot have a mass greater than about 1.4 times the mass of the Sun; beyond that limit the star collapses further, and the work brought him the Nobel Prize in Physics in…

India's first satellite was named after the ancient astronomer and mathematician Aryabhata, was built by the Indian Space Research Organisation and was launched in April 1975 from the Soviet Union, since India had no launch vehicle of its own at the time; it carried experiments in X-ray astronomy and solar…

It is a spiral galaxy of a few hundred billion stars, and the solar system lies in one of its spiral arms, far from the centre, which is why we see the galaxy edge on as a milky band across the night sky.

It appears brightest because it is both luminous and close, about 8.6 light years away, and it is in fact a binary system with a white dwarf companion.

A geostationary satellite is placed in a circular orbit about 35,786 kilometres above the equator, where its period of revolution equals the period of rotation of the earth about its axis, and it moves from west to east like the earth, so it appears to stay over the same point…

Being a red dwarf it cannot be seen with the naked eye, although it is the closest star to us after the Sun.

A light year is the distance travelled by light in vacuum in one year, which is about 9.46 times ten to the power twelve kilometres, or roughly nine and a half trillion kilometres.

A satellite is given the required height and speed by its launch vehicle, and after that no engine is needed: the gravitational pull of the earth alone acts on it and provides the centripetal force that keeps it in a curved path, so the satellite keeps falling towards the earth…

A star is so far away that it is a point source of light.

In the core of the Sun, at a temperature of about fifteen million kelvin, four hydrogen nuclei combine through the proton-proton chain to form one helium nucleus.

Cytokinins promote cytokinesis, that is cell division; kinetin was the first of them to be identified, from the degraded DNA of herring sperm, and zeatin, the natural form, was obtained from maize grains.