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Three vertical tubes A, B and C are attached to a horizontal pipe carrying a flowing liquid. At the points where A, B and C join, the pipe radii are 2 cm, 1 cm and 2 cm respectively. Compare the heights to which the liquid rises in the three tubes.
- in A is lesser than C
- in A and C is equal
- is same in all the three
- in A and B is same
Correct answer: in A and C is equal
Solution
By continuity the speed is highest where the pipe is narrowest (B), so pressure (and column height) is lowest there. A and C have equal radii, so equal speeds and equal pressures, giving equal column heights.
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