List of top Atmospheric Science Questions on Gravitation

Which one of the following is mathematical notation for precision? [where $\sigma$ is standard deviation]
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Optical disk drives are slower than magnetic disk drives. Reason (R): In optical disk, each sector has the same length regardless of its position from the center. In the light of the above statements, choose the most appropriate answer from the options given below :
The period of a satellite in a circular orbit of radius 12000 km around a planet is 3 hours. Obtain the period of a satellite in a circular orbit of radius 48000 km around the same planet.
Two satellites A and B go around a planet in circular orbits having radii of 4R and R, respectively. If the velocity of satellite A is 3v, the velocity of satellite B will be: