Quiz Preparation – UMD Racing e.V.

Quiz „General Engineering“

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1. Calculate the force Fc working at point C. Give answer in kN rounded to one decimal place.

Forces at point A: Rax = 3kN, Ray = 9kN, Ma = 10kN/m

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2. 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. 0 mins

b. 4 mins

c. 2 mins

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3. A spring in a car’s suspension has elastic potential energy store 226 J. If the spring constant is 8.1N/mm, find the extension. Give answer in meters to three significant figures.

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4. Three inductors are connected as shown in the following figure:

Given that L1 = 2L2, find L1 and L2 such that the equivalence inductance is L = 0.7 H.
Give your answers in Henry, rounded to three decimal places separated by a comma (L1, L2)

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5. Calculate the gravitational potential energy of a 4 kg object at 15 m above Earth’s surface with gravitational field strength of 9.81 N/kg. Give answer to three significant figures in J.

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A metal piece heated to

θ_1,M=1000∘C

with a mass of

M_M=6.5 kg

was cooled in a completely heat-insulated iron container filled with water. The mass of the water in the container is

M_W=10 kg

and the mass of the container is

M_B=2 kg.

The initial temperatures of the water and the container were the same and amounted to

θ_1,W=10∘C

. After complete thermal equilibrium between the immersed metal piece, the water, and the container, a temperature of

was established.
What is the average specific heat capacity of the metal piece

c

in the temperature range between

and

Input the result in kJ/(kg*K), round to 3 decimal numbers sperated by a point (example: 0.136).

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7. in m, to decimal numbers seperated by a point (example: 150.00), no unit requirment for the solution

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8. A lorry contains an engine with a power of 2.78 J/s. The lorry drives for 36 mins. Calculate the energy transferred in kJ rounded to three decimal places.

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9. 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.

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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. 281,7 m^2

b. 328,1 m^2

c. 314,12 m^2

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