Physics Quiz 4

Geostationary satellites orbit the earth at a fixed distance of 35,786 km. The speed of the satellite at this distance matches the earth's rotation, thereby keeping the satellite stationary over a particular point on the earth.

Decibel (db) is the unit used for the intensity of sound. The 'normal' hearing frequency range of a healthy young person is about 20 to 20,000Hz. Though a 'normal' audible range for loudness is from 0 to 180dB, anything over 85dB is considered damaging.

If the force is held constant the pressure is inversely proportional to the area (Pressure = force/area). Here area of the nail is much greater than the area of the needle. Thus, needle exerts more pressure than nail on the balloon.

A fountain pen works on the principle of gravity and capillary action. Capillary action is the phenomenon where a liquid will automatically draw itself along a very thin tube.

Farad is the unit of electrical capacitance (ability to hold an electric charge), in the MKS system of physical units. It is named in honour of the English scientist Michael Faraday.

The freezer in a refrigerator is fitted near the top so that it can cool the whole interior by setting up convection currents. The natural law of convection is that warm air rises while cold air falls, so the freezer at the top provides cold air for the other compartments at the bottom of the freezer.

Law of conservation of mass validates the statement that matter can neither be created nor destroyed. Matter can change form through physical and chemical changes, but through any of these changes, matter is conserved. The same amount of matter exists before and after the change—none is created or destroyed.

Energy of Ultraviolet rays is greater than Infrared rays. Radio waves have photons with the lowest energies. Microwaves have a little more energy than radio waves. Infrared has still more, followed by visible, ultraviolet, X-rays and gamma rays. Cosmic rays are (not part of the electromagnetic spectrum) high-energy outer space particles.

In economics, economic equilibrium is a situation in which economic forces such as supply and demand (internal factors) are balanced and in the absence of external influences, the values of economic variables will not change.

A simple microscope is a magnifying glass that has a single or double convex lens with a short focal length.