1) 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
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Answer
Explanation
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ANSWER: 0.0744 kW
Explanation:
No explanation is available for this question!
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2) 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
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Answer
Explanation
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ANSWER: 0.126 kW
Explanation:
No explanation is available for this question!
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3) Which of the following is not a property of lubricants?
a. High specific heat
b. High flash point
c. Low pour point
d. Low oxidation stability
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Answer
Explanation
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ANSWER: Low oxidation stability
Explanation:
No explanation is available for this question!
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4) What is the shear stress in fluid per unit velocity gradient called as?
a. Absolute viscosity
b. Dynamic viscosity
c. Both a. and b.
d. None of the above
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Answer
Explanation
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ANSWER: Both a. and b.
Explanation:
No explanation is available for this question!
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5) What is the S.I unit of kinematic viscosity?
a. N-s / m 2
b. m 2 / s
c. N-s m 2
d. None of the above
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Answer
Explanation
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ANSWER: m2 / s
Explanation:
No explanation is available for this question!
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6) Mass of ___________ required to neutralize one gram of lubricating oil is called as neutralization number.
a. potassium hydroxide
b. calcium hydroxide
c. magnesium hydroxide
d. None of the above
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Answer
Explanation
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ANSWER: potassium hydroxide
Explanation:
No explanation is available for this question!
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7) Which of the following parameters in Petroff's equation f = 2π2 (μns/p) (r/c) is/are dimensionless?
a. r/c
b. μn s/p
c. Both a. and b.
d. None of the above
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Answer
Explanation
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ANSWER: Both a. and b.
Explanation:
No explanation is available for this question!
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8) 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. 11.23 o C
b. 15.11 o C
c. 18.03 o C
d. 22.23 o C
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Answer
Explanation
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ANSWER: 18.03o C
Explanation:
No explanation is available for this question!
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9) Which of the following formula is used to calculate oil-film thickness in hydrodynamic bearings?
a. h = (c + Є cos θ)
b. h =(c – Є cos θ)
c. h = c (1+ Є sin θ)
d. h = c (1+ Є cos θ)
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Answer
Explanation
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ANSWER: h = c (1+ Є cos θ)
Explanation:
No explanation is available for this question!
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10) 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 speed = 900 rpm
5. Radial clearance = 150 microns
a. 0.2360
b. 0.0144
c. 0.0115
d. 0.0178
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Answer
Explanation
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ANSWER: 0.0144
Explanation:
No explanation is available for this question!
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