Apply Bernoulli principle one time at exit and at free surface of water and one.time at exit and point A u will get the desired answer.
How can you say va=vb
At B we neglect the velocity. And then from continuity a constant velocity will be established
Can someone explain why the liquid will flow upwards ?
Capillary action ? If yes shall we assume that the conditions are smooth enough for water to flow 2m upwards ?
Or is it that the question says the water is being filled through the tube ?
For syphon we have to initiate it , once initiated is flows on its own. Example sucking water from the tube initially