# Question Set 23

Q51. What is the difference between hard water and soft water?

Answer – Hard water contains an excess of scale forming impurities and soft water contains very little or no scale forming substances.

Q52. What is a Newtonian fluid?

Answer – A Newtonian fluid possesses a linear stress-strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

Q53. What is caustic embrittlement?

Answer – It is the actual physical change in metal that makes it extremely brittle and filled with minute cracks. It occurs particularly in the seams of riveted joints and around the rivet holes.

Q54. What are the points in the stress-strain curve for steel?

Answer – Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.

Q55. When is maximum discharge obtained in nozzle?

Answer – At the critical pressure ratio

Q56. How much is the work done in an isochoric process?

Q57. What does F.O.F. stand for in the piping design?

Answer – FOF stands for Face of Flange. A flange has either of the two types of faces:

a) Raised face
b) Flat face

The F.O.F is used to know the accurate dimension of the flange in order to avoid the minute errors in measurement in case of vertical or horizontal pipelines.

Q58. Explain Otto cycle.

Answer – Otto cycle can be explained by a pressure-volume relationship diagram. It shows the functioning cycle of a four-stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke. It was designed by Nicolas Otto, a German engineer.

Q59. What is the mechanism?

Answer – A mechanism is an assembly of different parts which perform a complete motion and is often part of a machine.

Q60. State the laws of thermodynamics

Answer – Thermodynamics is a physical science which studies the interrelation between heat, work and the internal energy of any system. Thermodynamics helps study all the systems of mechanical engineering. There are three laws of thermodynamics.

First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same.

Second Law: The second law of thermodynamics states that the entropy of any isolated system not in thermal equilibrium almost always increases.

Third Law: As the temperature approaches absolute zero, the entropy of a system approaches a minimum.