Physics Quiz 3

A rocket works on the principle of conservation of linear momentum. Rocket ejaculates gases in backward direction which creates momentum of the gases backward and thus by conservation of momentum, the rocket gets momentum in the forward direction making it move forward.

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.

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. The wavelength of the Visible Light ranges between 380 nm to 750 nm (3800 to 7500 angstroms). (The limits of the visible spectrum are not sharply defined but vary among individuals)

A convex mirror is used as a view-finding (side-view) mirror in a vehicle to see the traffic behind. This is because the image formed in a convex mirror is highly diminished due to which a convex mirror gives a wide field of view of the traffic behind the vehicle.

When a body is thrown upward, the height attained by that body is independent of the mass and depends on the initial speed of the body and the value of g. So, two stones of unequal masses are thrown vertically up with the same velocity they will reach the same height.

The working of the quartz crystal in the watch is based on Piezoelectric effect. Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress. A commonly known piezoelectric material is quartz.

The velocity of sound in the air does not change with the change of Pressure of gas (air). The speed of sound increases with the increase of the temperature of the medium.

Liquid water has one of the highest specific heat capacities among common substances, about 4184 J⋅kg⁻¹⋅K⁻¹ at 20°C; but that of ice, just below 0°C, is only 2093 J⋅kg⁻¹⋅K⁻¹. Hydrogen gas has more than three times (14300 J⋅kg⁻¹⋅K⁻¹) the specific heat as water under normal laboratory conditions.

A hygrometer is an instrument used in meteorological science to measure the humidity, or amount of water vapour in the air.

Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz. The frequency of ultrasound waves is above 20 kHz.