Physics - Study Mode

[#641] Stars are held together by
Correct Answer

(A) Gravitational forces

Explanation

Solution: A star is a sphere of gas held together by its own gravity. The closest star to Earth is our very own Sun, so we have an example nearby that astronomers can study in detail.

[#642] The minimum number of geostationary satellites needed for uninterrupted global coverage is :
Correct Answer

(A) 3

Explanation

Solution: In theory, 2 satellites in diametrically opposite geosynchronous orbits could cover the planet. In order for the satellites to communicate, a minimum of 3 would be needed, each at a 60 degree angle to the others. At this point, the strength and quality of coverage increases proportionally to the number of satellites.

[#643] The unit of noise pollution (level) is :
Correct Answer

(A) Decibel

Explanation

Solution: Loudness (also called sound pressure level, or SPL) is measured in logarithmic units called decibels (dB).

[#644] The speed of sound travel fastest through
Correct Answer

(B) Solid

Explanation

Solution: Of the three phases of matter (gas, liquid, and solid), sound waves travel the slowest through gases, faster through liquids, and fastest through solids.

[#645] Compressions and Rarefactions are characteristic of
Correct Answer

(A) Longitudinal waves

Explanation

Solution: Compressions and Rarefactions are characteristic of longitudinal waves.