What is cross-sectional data?

What is the difference between cross sectional data and Time series data?

Describe cross sectional data with their utility.

The ratio of lengths of two iron rods is 1:2 and that of their cross-sectional area is 2:3. What will be the ratio of their expansions in volume for the same rise in temperature?

Two conducting wires of lenghts l and 2l have the same cross-sectional area.Compare their resistances.

Two wires are made of the same material and have the same volume. The first wire cross sectional area A and the second wire has cross sectional area 3A. If the length of the first wire is increased by Delta l on applying a force F, how much force is needed to stretch the second wire by the same amount?

How does the resistance of a conductor depend on its length and cross sectional area?