Why is a railway track not a continuous piece but is made up of segments separated by the gaps?

Name the following : Animal whose body is made up of segments.

What is the resistance of one of the rails of a railway track 20 km long at 20^@ C? The cross section area of rail is 25 cm^2 and the rail is made of steel having resistivity at 20^@ C as made of steel having resistivity at 20^@ C as 6 xx 10^-8 Omega m.

Questions based on Paragraph : Seemas and shobha's mother asked both of them to take out 3 packs of 0.5 L of milk ( all at same temperature ) kept in refigerator and boil it . Seema took 1 l of milk in vessel A and shobha took rest of the milk in vessel B of same size as that of A . both the vessels are made up of same material and kept on the flame of equal intensity : Why is there a difference in the time taken to boil the milk in two vessels ?

Questions based on Paragraph : Seemas and shobha's mother asked both of them to take out 3 packs of 0.5 L of milk ( all at same temperature ) kept in refigerator and boil it . Seema took 1 l of milk in vessel A and shobha took rest of the milk in vessel B of same size as that of A . both the vessels are made up of same material and kept on the flame of equal intensity : After boiling , what can you say about the temperatures and heat content of the milk in both vessels ? why ?

Apparatus: Beakers. Chemicals: Samples of various metals , water. Procedure: Drop a piece of each of the metal in separate beakers filled with cold water. Which metal floats on water? Why?

Practice problems : A railway track is made from 25 m long iron rods . At temperature 20 ⁰C , the distance between two rods is 0.46 cm . Up to what temperature the tracks will be in proper condition to carry the trains ? [λ_iron = 11.5 x 10^-6 (1/ ⁰C) ]

A large ball 2 m in radius is made up of a rope of square cross section with edge length 4 mm. Negleting the air gaps in the balol, what is total length of the rope to the nearest order of magnitude?

Chapattis made from wheat only swell up but bread becomes spongy, soft and easy to digest. Why is it so?

Use your brain power Chapatis made from wheat only swell up but bread becomes spongy, soft and easy to digest. Why is it so?