Two equal-length springs are “nested” together in order to form a shock absorber. If it is designed to arrest the motion of a 2-kg mass that is dropped above the top of the springs from an at-rest position, and the maximum compression of the springs is to be 0.2 m, determine the required stiffness of the inner spring, K B if the outer spring has a stiffness k A = 400 N/m

(s) is unknown, please will you show all the working out. Thank you

Sketch a diagram of an air-water system that uses fan coils around the perimeter and an overhead air distribution system from a central air handler. Show the chiller, and water distribution pumps. Explain the operation of the system in summer season.?

A wet cooling tower is to cool 25 kg/sec of cooling water from 40oC to 25oC at a location where the atmospheric pressure remains constant at 97 kPa. Atmospheric air enters the tower at 25oC and 65% relative humidity and leaves saturated at 35oC. Neglecting the power input to the fan, determine the mass flow rate of the required makeup water.

Air flows in a pipe under fully developed conditions with an average velocity of 1.25 m/s and a temperature of 16°C. The pipe’s inner diameter is 4 cm, and its length is 4 m. The first half of the pipe is kept at a constant wall temperature of 100°C. The second half of the pipe is subjected to a constant heat flux of 200 W. The properties of air at 80°C are ρ = 0.9994 kg/m³, k = 0.02953 W/m·K, v = 2.097 × 10^–5 m²/s, c_p = 1008 J/kg·K, and Pr = 0.7154.

Determine the wall temperature at the exit of the tube.

A hot-rolled steel bar is subjected to a repeated axial tensile load as shown. The material has ultimate tensile stress S_ut=1300MPa. The bar has a diameter of 30mm. The notch sensitivity factor, theoretical stress concentration factor, and factor of safety are q=0.52,K_t=2.42 and n=1 respectively. Find the maximum force F that the bar can carry for 10^4 cycles at 90% reliability

Figures                                                                10 Points

Endurance limit                                                   10 Point

Endurance strength                                             10 Points

Fatigue stress concentration factor                      5points

Determination of force                                        15points

Describe the intake process of a naturally aspirated diesel engine by means of: a. Show the intake (suction) process by drawing the valve timing diagram with respect to TDC and BDC. b. What is the importance of intake valve opening crank angle bTDC c. What is the importance of intake valve closing crank angle aBDC

25. A turbojet engine gets most of its thrust from an airflow that bypasses the combustor and turbine sections.   a. True b. False


26. A turboprop engine gets most of its thrust from an airflow that bypasses the combustor and turbine sections. a. True b. False

27. In a gas turbine engine for aircraft applications, a diffuser is needed at the inlet to … a. Reduce the speed of the air entering the compressor section to near zero relative to the compressor air intake. b. Reduce the pressure of the air entering the compressor. c. Increase the temperature of the air entering the compressor.   d. Reduce heat transfer from the air to the surroundings, as this heat will be of value in the engine.

1. The dependent variable has a score in the case of logistic regression. TRUE or FALSE and why?

2, If the probability of an even A is 0.2 and that of an event B is 0.10 then the odds ratio is: a.1 b. 2.25 c. 2.0 d. 0.5

3. In the case of logistic regression, we estimate how much the natural logarithm of the odds for Y =1 changes for a unit change in X. TRUE or FALSE

4. In binomial logistic regression, the dependent variables consists of more than two categories. TRUE or FALSE and why?

5. Similar to linear regression, logistic regression has one or more independent variables. TRUE or FALSE and why?

A flat surface is made up of electrically heated strips of length 1m and width 0.05m. The strips, which are electrically insulated from one another, are laid with their long sides in contact and an airstream at 25°C flows over the surface in a direction normal to long sides of the strips at a velocity of 65 m/s. Electrical power is supplied individually to each of the strips such that they all have a surface temperature of 229°C. Determine which strip requires the most power. At 400 K, k = 0.0331 W/m·K, ν = 2.610-5 m2·s, ρ = 0.883 kg/m3, Cp = 1013 J/kg·K, Pr = 0.709.

(c) A 50 mm-diameter propeller was installed in a 150 mm-diameter water pipe and the propeller speed was measured for a range of water discharge in the pipe. The water had a density and dynamic viscosity of 1000 kg/m³ and 0.00112 Ns/m² respectively. The measured results were as follows:

Plot the dependence of propeller coefficient against propeller Reynolds number. A geometrically similar propeller with diameter 100 mm was installed in a 300 mm-diameter pipe conveying oil with density 800 kg/m³ and dynamic viscosity 0.007 Ns/m² . Estimate the discharge in the oil pipe for measured propeller speeds of 40 rps and 90 rps.

Producers of metal powders started producing special metal powders for the powder-bed fusion method (such as SLS) of additive manufacturing. Manufacturing companies are advised not to use conventional metal powders for additive manufacturing. Using rational analysis, explain why.

An electrical resistance heater embedded in thin walled tube provides 71 kW of uniform heating to increase the water temperature from 25°C to 75°C. Water enters the circular section of diameter 101 in cm, at a velocity 101 in cm/s. Heat loss to the surroundings is perfectly stopped by an insulation on the outer surface of the heater hence, all the heat dissipated by the heater is transferred to the flowing water in the tube. By analyzing the internal flow convection heat transfer and determine the length of the tube and the surface temperature at the exit of tube? The properties of water at the bulk mean temperature are ?= 1000 kg/m3, Cp= 4100 J/kg-K, k=0.631 W/m-K, Pr= 4.32, ?=0.658×10-6 m2/s.