Question 19N.3.HL.TZ0.9

air speed at A greater than at B/speed at B is zero
OR
total/stagnation pressure «P_B» – static pressure «P_A» = dynamic pressure ✔

so P_A is less than at P_B (or vice versa) «by Bernoulli effect» ✔

height of the liquid column is related to «dynamic» pressure difference «hence lower height in arm B» ✔

«${\rho }_{\mathrm{liquid}} gh=0.5\times {\rho }_{\mathrm{air}} v^2$»

difference in pressure $P_{\mathrm{B}}-P_{\mathrm{A}}=8.7\times {10}^2\times 9.8\times 0.06=510$ «Pa» ✔

correct substitution into the Bernoulli equation, eg: $\frac{1}{2}\times 1.2v^2=510$ ✔

$v=29$ «ms^–1» ✔