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BIT QUESTIONS - Tribology

1. Starting friction is low in [ ]a) Hydrodynamic lubrication b) hydrostatic lubricationc) Boundary lubrication d) mixed lubrication

2. Coefficient of friction in a journal bearing is a function of [ ]a) N/p b) R/c c) l/d d) all the above

3. When the length of bearing is equal to its diameter it is called [ ]a) Long bearing b) short bearing

c)Medium bearing d) square bearing

4. The most suitable bearing for resisting heavy loads at slow speeds is [ ]a) Hydrodynamic bearing b) hydrostatic bearing

c)Roller bearing d) ball bearing

5. In a journal bearing the following part rotates [ ]a) Journal b) bearing c) both d) any of above happen

6. The axis of shaft rotating clockwise in the journal tends to movea) Towards bottom b) into fourth quadrant c) into third quadrant

7. Oil whirl or whip may happen in the following type of bearing [ ]a) hydrodynamic b) hydrostatic c) pivoted d) all the above

8. Oil whip can occur if the whirling speed is [ ]a) Low b) high c) equals speed of rotation d) half the speed of rotation

9. Bearing characteristic number is [ ]a) N/p b) p/N c) /pN d) pN/

10.Teflon is used in bearings because [ ]a) Low coefficient of friction b) bondability

c)It does not absorb moisture d) all the above

11.The unit of dynamic viscosity in CGS system is ------------------------12.The unit of dynamic viscosity in SI system is ------------------------13.The unit of kinematic viscosity in CGS system is ------------------------14.The unit of kinematic viscosity in SI system is ------------------------15.Number of viscosity grades used in ISO standard is ------------------------16.The most significant forces in Reynolds hydrodynamic analysis are [ ]

a) body forces b) surface forces c) inertia forces d)random forces

17.In a long hydrodynamic bearing pressure varies only in [ ]

a) X-direction b) Y-direction c) Z-direction d) none of above

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18. velocity gradient is maximum in in hydrodynamic bearings in [ ]

a) X-direction b) Y-direction c) Z-direction d) none of above

19.The pressure value in Sommerfeld number is [ ]

a) peak pressure b) average pressure c) minimum pressure

20. coefficient of friction is minimum in the following type of lubrication [ ]

a) boundary b) mixed c) hydrodynamic d) dry friction

21. The first term in Reynolds hydrodynamic lubrication analysis relates to -----------------------------

22. The second term in Reynolds hydrodynamic lubrication analysis relates to ------------------------

23. The third term in Reynolds hydrodynamic lubrication analysis relates to---------------------------

24.One centipoise is --------------------------- Pascal seconds

25. --------------------------------------- is an example of pseudoplastic material.

26. --------------------------------------- is an example of dilatant material

27.O

ne m

2

/sec = ----------------------------------- centiStokes28. Redwood viscometer measures -------------------------------------

29. Falling sphere viscometer measures ----------------------------------------

30.The chemical formula ofTeflon is --------------------------------------------------------

31.Thermal coefficient of expansion of plastics is more / less than that of metals.

32.Coefficient of friction ofTeflon is about ---------------------

Answers:

1.b 2.d 3.d 4.b 5.d 6.c 7.a 8.d 9.a 10.d 11.Poise

12.Pascal second 13. Stokes 14. m2/sec 15.18 16.b 17.a 18.b 19.b

20.c 21.wedge action on fluid 22. elastic deformation of boundary 23. Squeeze film

action of fluid 24.0.001 25. Paint or shampoo 26. Wet sand 27.One million

28. Kinematic viscosity 29. dynamic viscosity 30. Poly tetra floro ethylene 31. More

32.0.04