The prefix 'pico' represents MCQ with Answer and Explanation

Explanation:
Seismograph detects and records ground motions caused by earthquakes, volcanic activity, or explosions. It measures seismic waves (P-waves, S-waves). Barometer detects pressure changes; hydrophone detects underwater sound; magnetometer detects magnetic fields. Memory tip: 'Seismo = earthquake (like seismology)'. This instrument-application question tests knowledge of geophysical tools, frequently examined in competitive exams. Always associate instrument names with their field of use: seismograph (geology), barometer (meteorology), etc.

Explanation:
F ∝ 1/r², so if r→3r, F→F/9.

Explanation:
A geostationary satellite must appear stationary to an observer on the Earth's surface. To achieve this, it must orbit in the exact equatorial plane and strictly follow the Earth's rotation. Since the Earth rotates on its axis from West to East, the geostationary satellite must also orbit from West to East.