Correct Answer to Question 9

If we consider point A as one end of a tube of flow that begins at the top surface of the water, and point B as the other end of the tube of flow, we can apply Bernoulli's equation to solve for the velocity at point B. At points A and B, the pressure is atmospheric pressure, so P_A = P_B, and Bernoulli's equation becomes:

(1/2) V_A² + g Y_A = (1/2) V_B² + g Y_B .

The density cancells in the equation, and if the tank is very large, the velocity at point A is essentially zero (since the water level changes only slowly there). Thus we can solve for V_B:

V_B = sqrt(2g(Y_A - Y_B)) ,

where

Y_A - Y_B

is the height above the efflux tube, which is 5 m in our case.

Formula Sheet

Question 9

Question 10

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