Determine the Sommerfeld number considering the following data for hydrodynamic bearing?
1. Diameter of bearing = 120 mm 2. Bearing pressure = 5 N/mm2 3. Oil viscosity = 30 cP 4. Journal spee…
Mechanical Engineering (MCQ)
Which of the following formula is used to calculate oil-film thickness in hydrodynamic bearings?
a. h = (c + ? cos ?) b. h =(c – ? cos ?) c. h = c (1+ ? sin ?) d. h = c (1+ ? cos ?) ANSWER: h = c (1+ …
Lubricating oil used in hydrodynamic bearing has total flow rate of 0.340 l/min and side leakage of 0.1520 l/min. If mass density of oil is 600 kg/m3 and specific heat is 1.05 kJ/kg oC, what is the rise in temperature if power lost in friction is 0.05 kW?
a. 11.23o C b. 15.11o C c. 18.03o C d. 22.23o C ANSWER: 18.03o C
Lubricating oil of mass density 800 kg/m3 used in 360o hydrodynamic bearing has a flow rate of 6000 mm3. Neglecting side leakage if temperature rises to 10 oC and specific heat is 1.55 kJ/kg oC, what is the rate of heat dissipated in the bearing?
a. 7.4 W b. 236 W c. 0.236 kW d. 0.0744 kW ANSWER: 0.0744 kW
A journal of 120 mm diameter rotates in a bearing at a speed of 1000 rpm. What is the power lost during friction if 8 kN radial load acts on the journal and coefficient of friction is 2.525 x 10-3?
a. 0.126 kW b. 0.253 KW c. 2.365 kW d. 7.615 kW ANSWER: 0.126 kW
What does number 6 indicate in the class of wire rope 6 x 37 (18/12/6/1)?
a. Diameter b. Strands c. Wires d. None of the above ANSWER: Strands
Lang lay ropes offer more resistance to __________
a. fatigue failure b. abrasive failure c. both a. and b. d. none of the above ANSWER: both a. and b.
A V-belt pulley has belt velocity 20 m/s and mass 0.7 kg per meter. If allowable tension in the belt is 600 N then what will be the power transmitting capacity of belt?
(Assume µ = 0.5 & ? = 2.5 rad) a. 3.75 kW b. 3.2 kW c. 4.5 kW d. 5.23 kW ANSWER: 4.5 kW
A V-belt pulley transmits power to flat belt pulley. If the coefficient of friction is 0.25 then which pulley governs the design? (ß = 21o & a = 0.2)
a. Flat pulley b. V-belt pulley c. Both a. and b. d. None of the above ANSWER: Flat pulley
Which of the following statements is/are true for V-belts?
a. V-belt drives have low reduction ratio b. Due to wedging action slip is negligible in V-belts c. V…
A gear box having surface area of 0.30 m2 has overall heat transfer coefficient of 23 W/m2 oC,when a fan is mounted on worm shaft to circulate air on fins. What is the power transmitting capacity of a gear box based on thermal considerations, if temperature rise of lubricating oil is 50 oC? (Assume λ = 6o, Φn = 22o & μ = 0.05)
a. 1.023 kW b. 1.006 kW c. 1.227 kW d. 2.000 kW ANSWER: 1.006 kW
What is the axial force acting on a worm gear for a worm gear pair 1/40/9.5/10, if tangential and axial force of 6213 N and 9236 N act respectively on the worm? ( Φn = 25o & μ = 0.04)
a. 6213 N b. 9263 N c. 3050 N d. Insufficient data ANSWER: 6213 N
If pressure angle is 22o and coefficient of friction is 0.05. What is the axial force acting on the worm gear designated as 1/40/10/5, if tangential force of 1200 N acts on it?
a. 1241.2 N b. 2618.4 N c. 7755.1 N d. 7847.4 N ANSWER: 7755.1 N
What is the shortest distance between worm gear and axes of the worm for a worm gear pair designated as 2/40/10/8?
a. 50 mm b. 200 mm c. 320 mm d. 360 mm ANSWER: 200 mm
A worm gear pair has 2 starts on worm thread, 11.2 as diametral quotient, 2 as module and 38 number of teeth on worm gear. How is the gear pair designated with these specifications?
a. 2/11.2/38/2* b. 11.2/2/38/2 c. 2/38/2/11.2 d. 2/38/11.2/2 ANSWER: 2/38/11.2/2
A cylindrical roller bearing is subjected to radial force of 4500 N and application factor 1.3. What is the equivalent dynamic load acting on bearing if it has 90% reliability with desired life of 10000 hrs?
a. 3461.53 N b. 5000 N c. 5850 N d. Insufficient data ANSWER: 5850 N
Which of the following bearings carry thrust load in one direction?
a. Spherical roller thrust bearings b. Taper roller bearings c. Both a. and b. d. None of the above ANS…
Which of the following elements is not used as a roller in roller bearings?
a. Cylindrical b. Taper c. Spherical d. None of the above ANSWER: None of the above
Load acting on bearing in its plane of rotation is called as __________
a. axial load b. radial load c. thrust load d. none of the above ANSWER: radial load
A deep groove ball bearing rotating at 1200 r.p.m. is subjected to radial and an axial force of 2000 N and 1500 N respectively. What will be the basic dynamic capacity of bearing if 20,000 hours is the rating life?
(Consider radial factor = 0.55, Thrust factor = 2 & application factor = 1.5? a. 69.448 kN b. 54.…