Mechanical Knowledge

THERMODYNAMICS QUESTION SOLUTION, CHAPTER. ENERGY INTERACTION. Question 1. A spherical balloon of 1m diameter contains a gas at 150 KPa. The gas inside balloon is heated until pressure reaches 450 KPa. During the process of heating the pressure of gas inside the balloon is proportional to cube of the diameter of the balloon. Find the work done by the gas. Solution: D1= 1 m    P1= 150 KPa                                           V = (4/3)  π R^3 =    πD^3/6        P2 = 450 KPa                                             dV = ( π/6)  (3D^2)    δD P directly proportional D^3                         dV = ( π/2) (D^2)   δD P = k(D^3)                                                   W =  ∫ P dV  --------------(0) P1=k(D1^3)                                                  150 = k(1)^3                                              k = 150 KN/m^3 ----------------(1)                P2 = k(D2^3) 450 = 150(D2)^3 D2 = 1.44 m -----------------------(2) W =  ∫ P dV  W =  ∫ (kD^3)   ( π/2) (D^2)   δ

 Q1. If LSU has no tin ball what we have to do. (a) confirm is ball need to fill  (b) add tin ball (c) move solder nozzle (d) none of the above Ans: (a) Q2. Which command we have to use if computer screen shows tester is running in background. (a) alt+tab+esc (b) shift+ctrl+esc (c) ctrl+shift+esc (d) esc+shift+ctrl Ans (c) Q3. What are the benefits of nitrogen in soldering? (a) Better wetting (b) less heat (c) both A and B (d) none of the above Ans (c) Q4. What are the measure concern when clean a laser lens? (a) follow steps (b) make sure nitrogen and air pressure is not on (c) take some time (d) all of the above Ans (b) Q5. How much approximate pressure need before to spray ball on module (a) 1722mbar (b) 1500mbar (c) 1054mbar (d) 2001mbar Ans (c) Q6. How many main pressure gauges in soldering machine? (a) 5 (b) 7 (c) 8 (d) 2 Ans (d) Q7. What is the meaning of number1 blue color at the time soldering process on HMI screen? (a) module is not there (b) module is there or module pin sca

 Q1. Which of the following case soldering nozzle is block? (a) Laser center is not correct (b) Module lift up before soldering (c) Ball center is not correct (d) None of these Ans (b) Q2. Which switch used to move socket at CCD position (a) Positioning camera (b) Positioning location (c) Move (d) All of the above   Ans (a) Q3. How many levels ball need to fill in soldering?  (a) Half (b) Full (c) Semi half (d) none of these Ans (a) Q4. What metal is the solder ball made of  (a) iron (b) tin (c) Both A and B (d) None of these Ans  (b) Q5. what should we do, if jig did not sense by left and right station? (a) Check jig is placed flat (b) Check proximity sensor of the center fixture is loose or offset  (c) Check jig and press emergency  (d) All of the above Ans (a) Q6. What we have to do if computer screen shows us image timeout. (a) Press emergency (b) Restart the CCD positioning camera (c) Press home switch (d) Power off/ power on Ans (b)

 THERMODYNAMICS  Chapter 1. ZEROTH LAW OF THERMODYNAMICS  Q1. Most of the real processes are (a) quasi-static (b) non-quasi-static (C) adiabatic  (d ) isothermal  Ans:(b) non-quasi-static Q2. A system comprising of a single phase is called  (a) closed system (b) open system (c) heterogeneous system (d) homogenous system Ans: (d) homogenous system Q3.when mean free path of the molecules of a gas approaches the order of magnitude of the dimensions of the vessel, which concept of the following loses its validity? (A) continuum (B) stability  (C) equilibrium  (D) entropy  Ans: (A) continuum Q4. Which of the following is not a point function. (A) temperature  (B) pressure (C) power (D) energy Ans: (C) power Q5. The absolute zero pressure will be. (A) when molecular momentum of the system becomes zero (B) at sea level (C) at a temperature of -273.15K (D) under vacuum conditions Ans: (A) when molecular momentum of the system becomes zero  

 THERMODYNAMICS  Chapter 1. ZEROTH LAW OF THERMODYNAMICS Question2. A new temperature scale N is to be defined. The boiling and freezing points of water on this scale are 100°N amd 400°N respectively. Then (a) what will be the reading on the new scale corresponding to 60°C? (b) At what temperature both the Celsius and new temperature scale reading would be same? Sol: ts= boiling temperature  ti= ice temperature  tc=corresponding temperature   scale reading:         boiling temperature    corresponding          freezing temperature  new scale                             100°N                       x°N                            400°N Celsius scale                         100°C                       60°C                           0°C Celsius scale = new scale ts - ti/ts - tc     =  ts - ti/ts - tc   100 - 0/100 - 60 = 100°N - 400°N/100°N - X°C 100/40 = -300°N/100°N - X°N 100°N - X°N = -120°N    X = 220°N (b)  both Celsius and new temperature scale value same at 100°