Which one of the following force is non-central and non-conservative?

Consider the following statements relating to Richter scale.

1. It was devised in 1935 by Charles F. Richter.

2. It describes the quantity of energy released by a single earthquake.

3. Richter scale has no upper limit.

Which of the statement(s) given above is/are correct?

Suppose there are two planets, 1 and 2, having the same density, but their radii are R₁ and R₂ respectively, where R₁ > R₂. The accelerations due to gravity on the surface of these planets are related as

The sun is seen little before it rises and for a short while after it sets. This is because of