Mechanical Engineering Answers

2. Two liquids of different densities (ρ 1 = 1550 kg m /m 3 and ρ 2 = 550 kg m /m 3 ) are poured together in a

cylindrical container 0.5 m in diameter x 1 m height. If the resulting density of the mixture is 850 kg m m 3 ,

determine a) the mass of each liquid inside the tank (kg m ), b) the weight of the mixture in kg f if g = 9.79

m/s 2 .

1. The weight of a piece of metal is 225 lb f at a location where gravitational acceleration is 31 ft/s 2 . Find the weight of the metal in lb f and the mass of the metal in lb m if it will be placed on the surface of the moon where g is 5.5 ft/s 2 .

Background A villager in South Africa has an inhabitant of five hundred people. It is 200 km from the nearest Eskom substation based on line of sight. Presently, the only source of electric power in the village is diesel generator. Due to Covid-19, the company that used to maintain the generator has folded up, consequently, the villagers have no electricity. Aim Design a standalone (off grid) Photovoltaic (PV) system with special reference to the village in South Africa with the following PV panel generation factors: Group Number PV panel generation factor of 7.Please refer to the table below for the aspects that need to be covered on the project. Item Description 1 Project aim 2 Project theoretical background 3 Project problem statement 4 Specifications (material to be used for the project) 14 Project layout (block diagram) 15 Recommendations 16 Conclusion

Which of the following is NOT the heat engine cycle

a. refrigerator

b. stem power plant

c. mass of gas confined in a cylinder and piston machine

d. none of the above

First law of thermodynamics provides

a. a statement that energy balance occurs when a system undergoes the change of state or the process

b. a statement about whether the change of state or the process is at all feasible or not

c. both a. and b.

d. none of the above

Pick up the correct statement from the following:

A. For thin structures subjected to wetting and drying, the water cement ratio should be 0.45

B. For mass concrete structures subjected to wetting and drying, the water ratio should be 0.55

C. For thin structures which remain continuously under water, the water-cement ratio by weight should be 0.55

D. For massive concrete structures which remain continuously under water, the water cement ratio by weight should be 0.65

An elastic linear spring of spring constant 144 N/cm is compressed from an initial unconstrained length to a final of 6cm. If the work required on the spring is 648J, determine the initial length of the spring in centimeters:

Steam at 15 bar and 250oC is expanded reversibly in a closed system to 5 bar. At this pressure the steam is just dry saturated. For a mass of 1 kg calculate the following.

i. The final volume.

ii. The change in internal energy.

iii. The work done.