Question
For Questions 17, 18, please refer to the problem statement below. Please indicate your answers on the Multiple Choice Answer Sheet on page 2. Problem Statement: A 2 mm internal diameter U-tube containing water is initially sealed on one end. A 10 mL volume of ethyl alcohol is added to the tube through the open end as shown in the figure below. The tube is maintained at a temperature of 20 degree C. What is the height difference between the water levels in the manometer? 0.24 mm 0.72 mm 2.4 mm 7.2 mm What is the height difference between the water levels if the seal is removed? 0.13 cm 1.30 cm 0.25 cm 2.50 cm For Questions 19, 20 and 21, please refer to the problem statement below. Please indicate your answers on the Multiple Choice Answer Sheet on page 2. Problem Statement: Consider a tank filled with mercury at 20 degree C (rho = 13,550 kg/m3) and accelerating while rolling up a 35 degree inclined plane, as shown in the figure below. Assuming rigid body motion, answer the following questions: The absolute value (i.e. the magnitude) of the tank's acceleration is: 4.34 m/s2 5.82 m/s2 8.82 m/s2 The tank is: accelerating decelerating moving with a constant velocity The pressure at point A is: 38,548 Pa 35,114 Pa 31,576 Pa For Questions 22, 23, 24, please refer to the problem statement below. Please indicate your answers on the Multiple Choice Answer Sheet on page 2. Problem Statement: A rigid tank of volume 1 m3 is initially filled with air at 20 degree C and 100 kPa. At the start of, time t = 0, a vacuum pump is turned on and begins to evacuate air at a contact volume flow rate of 80 L/min (rate is independent of the tank's pressure). Assume an ideal gas and an isothermal (constant temperature) evacuation and: Set-up a differential equation for mass flow out of the tank. This should be of the form: Vdrho/dt + rhoQ = 0 where rho is the air's density at any time, V is the tank's volume and Q is the volume flow rate out-off the tank m(t) = m0-dm/dtt where m0 is the initial mass of air within the tank and m(t) is its value at any time after the pump has been started d/dt(rhoQ) + rhoQ = 0 where rho is the air's density at any time and Q is the volume flow rate out-off the tank Solve this equation for the time t as a function of the tank volume V, gas volume flow rate Q, initial tank pressure rho and the final tank pressure p0. The answer should be in the form: t = -V/Qln(p/p0) t = V/Q(p/p0 - 1) t = -V/Qln(pQ/RT) The time (in seconds) to pump the tank down to a pressure of p = 20 kPa would be: 1,200 s 3,000 s 200 s For Questions 25, 26, 27 please refer to the problem statement below. Please indicate your answers on the Multiple Choice Answer Sheet on page 2. Problem Statement: Aim diameter tank, having a mass of 50 kg when empty, is placed on a scale as shown in the figure. The tank is being filled with room-temperature water at the rate of 100 L/s, through an opening in the top. At the same time, water is draining from the tank through two small pipes of 10 cm in diameter, near the bottom. The diameter of the inflow jet is 20 cm. Assuming that the velocity of an outflow from a small pipe can be calculated from: v = (2gh)1/2, where "h" is the depth of the water in the tank, and "g" is the gravitational acceleration, answer the following questions: When the volume of the water in the tank reaches 200 L, what would be the rate of change of the water level inside the tank: 0 cm/s 4.96 cm/s 8.3 cm/s 12.1 cm/s How much water has been accumulated in the tank by the time the steady state condition is reached (i.e. when the water level would remain unchanged)? 1,620 L 1,507 L 856 L 2,143 L At steady state flow, the scale reading would be closest to: 55 kg 762 kg 2,158 kg 1,648 kg
Explanation / Answer
options with their answers:
17)b 18)a 27)b
19)b 20)a
21)a 22)c
23)b 24)b
25)c 26)d
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