The velocity of liquid coming out of a small hole of a large vessel containing two different liquids shown in figure is

 

A railway track (made of iron) is laid in winter when the average temperature is $18°C.$ <!-- [if gte mso 9]><xml> </xml><![endif]--> The track consists of sections of 12.0m placed on after the other. How much gap (in cm) should be left between two such sections so that there is no compression during summer when the maximum temperature goes to $48°C?$ <!-- [if gte mso 9]><xml> </xml><![endif]--> Coefficient of linear expansion of iron = 11 × $10^{-6}/°C$ <!-- [if gte mso 9]><xml> </xml><![endif]-->.