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Question 19N.3.HL.TZ0.9a

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Date November 2019 Marks available [Maximum mark: 3] Reference code 19N.3.HL.TZ0.9a
Level HL Paper 3 Time zone TZ0
Command term Explain Question number a Adapted from N/A
a.
[Maximum mark: 3]
19N.3.HL.TZ0.9a

A Pitot tube shown in the diagram is used to determine the speed of air flowing steadily in a horizontal wind tunnel. The narrow tube between points A and B is filled with a liquid. At point B the speed of the air is zero.

(a)

Explain why the levels of the liquid are at different heights.

[3]

Markscheme

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

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

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

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