General Science GK Questions with Answers – Page 120

The pressure at a point inside a liquid equals the depth multiplied by the density of the liquid and by the acceleration due to gravity.

In 1798 Cavendish used a delicate torsion balance to measure the extremely small attraction between lead spheres in a laboratory and from it obtained a value of G, about 6.674 times ten to the power minus eleven newton metre squared per kilogram squared.

A mercury barometer balances the pressure of the atmosphere against a column of mercury, which stands about 76 centimetres high at sea level.

Weight equals mass times the acceleration due to gravity, and the acceleration due to gravity on the moon is about one-sixth of its value on the earth because the moon has a much smaller mass and a smaller radius.

It states that a body immersed wholly or partly in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced, so the apparent loss in weight of the body equals the weight of the displaced fluid.

Pascal's law states that pressure applied to an enclosed fluid is transmitted undiminished in every direction to all parts of the fluid and to the walls of the container.

Escape velocity is the minimum speed a body must be given so that it leaves the gravitational pull of the planet and never returns.

The earth is flattened at the poles, so the distance from the centre is least there, and since g varies inversely as the square of that distance, g is largest at the poles.

Pressure is thrust per unit area, so its unit is one newton per square metre, and this unit is named the pascal after Blaise Pascal.

The name itself says so: in Greek arthros means jointed and podos means foot, so arthropods are the animals with jointed legs.

Argon is a noble gas whose outer shell already holds eight electrons, so it has no room to take another one easily; adding an electron would mean starting a new shell, and energy has to be supplied rather than released.

Leucoplasts are the colourless plastids of plant cells, and each kind is named after what it stores.

At the top the object holds only potential energy; as it falls, that store is steadily converted into kinetic energy, and just as it touches the ground almost all of it is kinetic.

Plants respire day and night, breaking glucose down to release energy, and carbon dioxide is the waste product of that process.

The same magnet moves at the same speed in both cases, so the rate of change of magnetic flux through the coil is equal and the induced potential difference has the same magnitude.

Fibrous roots are the mark of monocotyledonous plants such as wheat, maize, rice and grasses, not of dicots.

The work done in moving a charge across a potential difference is W = QV, so W = 5 × 16 = 80 joules.

The peacock is a bird, and all birds, like mammals, have a heart of four chambers: two atria and two ventricles.

Zinc has atomic number 30, which means each of its atoms carries 30 protons in the nucleus.

It states that the upthrust on a body dipped fully or partly in a fluid equals the weight of the fluid the body pushes aside.