Quiz Preparation – UMD Racing e.V.

Quiz „General Engineering“

1 / 10

In a cylinder, air is compressed isothermally at ambient temperature (

θ_U=20∘C)

p_{1} = 0.1 MPa

p_{2} = 0.5 MPa

Calculate the change in the specific entropy of the air in the cylinder.

Round to two decimal numbers sperated by a point. Input in J/(kgK). (Example -365.26)

p2 = p1 * (V1/V2)^gamma
gamma= 1.4

2 / 10

An air as an ideal gas expands adiabatic from a volume of V1 = 1,00l with its pressure of p1 = 10^5 Pa to 1/10 of its original pressure. What volume V2 (in litres) does the gas reach after it’s expansion? Round to two decimal places

3 / 10

A lorry contains an engine with a power of 0.255 W. The lorry drives for 51 s. Calculate the energy transferred in Joules and round to one decimal places.

4 / 10

Answer in MJ, round to one decimal number (example 45.7), no unit in the answer

5 / 10

How high (in m) can a column of liquid be lifted by a reciprocating piston, neglecting leakage and losses, if the air pressure is 101300 Pa and the pressure p₁ approaches zero?

Example Input 14.3 (use a point, no unit)

6 / 10

An air stream

dot{M}_L = 5.5 kg/s,

cp_L=1 kJ/(kgK)

is to be heated in a plate heat exchanger from

θ_L′=20∘C

θ_L′′=150∘C

. For this purpose, a flue gas stream

dot{M}_R = 7.22

cp_R=1.1 kJ/(kgK)

with a temperature of

θ_R′=300∘C

is available. The overall heat transfer coefficient is

W/(m^2*K)

.
What is the required heating surface AAA if the fluid streams are arranged in counterflow?

a. 314,12 m^2

b. 281,7 m^2

c. 328,1 m^2

7 / 10

You would like to drink a cup of very hot coffee with milk early in the morning, but you
are in a hurry and have only 5 minutes until you have to leave for work. At which time
after brewing should you add the cold milk to the coffee and stir in order to decrease the
temperature of the mixture as much as possible:
a) 0 minutes (immediately),
b) 2 minutes, or
c) 4 minutes?
Suppose that the stirring can be done instantaneously and that you need the last one
minute for drinking.

brew temperature C = 80 ◦C, temperature of milk = M = 10 ◦C, room temperature
0 = 20 ◦C, volume of coffee VC = 300 ml, volume of milk VM = 100 ml, specific heat
capacity of coffee cC = 4180 J/(kgK), specific heat capacity of milk cM = 3500 J/(kgK).

Please enter only the letter of the corresponding answer

a. 2 mins

b. 0 mins

c. 4 mins

8 / 10

An object is fired vertically upwards from the ground at time t = 0 s in still air at a speed of 8.0 m/s. On the way up, what is the height of the object above the ground when it has a speed of 2.0 m/s. At what time does it reach this height on the way down? Give both answers separated by a comma to one decimal place.

9 / 10

In a gas pipe, the gas pressure pG is measured using a U-tube manometer connected at the bottom. Above the meniscus of the measuring liquid (mercury with density ρQ) on the gas side, there is a column of water with height h₂ and density ρW.
Question:
What negative pressure △pU (vacuum) exists in the pipe compared to the external pressure p₀?

Result in Pa, two decimal numbers seperated by a point (exp. 15.3). Do not put the Unit in the field below.

10 / 10

What temperature would occur at the stagnation point of an aircraft flying at a speed of

V_{1} = 2000 km/h

, assuming that the air behaves as an ideal gas under these conditions? The temperature of the undisturbed air is theta_1 = -30°C.

a. 308,.64°F

b. 254.53°F

c. 177.06°F

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