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SRI RAMAKRISHNA INSTITUTE OF TECHNILOGY, COIMBATORE-10

DEPARTMENT OF MECHANICAL ENGINEERING

TWO MARKS Q&A

SUBJECT: KINEMATICS OF MACHINERY YEAR/SEM: II / III

UNIT-V-FRICTION

1. Define clutch.Clutch is a transmission device of an automobile which is used to engage

and disengage the power from the engine to the rest of the system.

2. What are the types of friction clutches?Types of friction clutches are:Disc or plate clutches.Cone clutches.Centrifugal clutches.

3. Define centrifugal clutch.Centrifugal clutch is being increasingly used in automobile and machinesobviously it works on the principle of centrifugal force.

4. What are the types of flat drives?The types of flat drives are:Compound belt drive.Stepped or cone pulley drive.Fast and loose pulley.

5. Define slip.Slip is defined as the relative motion between the belt and pulley.

6. Define law of belting.

Law of belting states that the centre line of the belt, as if approaches thepulley lie in a plane perpendicular to the axis of that pulley or must lie inthe plane of the pulley otherwise the belt will run off the pulley.

7. Rope drive: Utility.The rope drives are widely used when large power is to be transmittedcontinuously from one pulley to another over a considerable distance. Oneadvantage of rope drives is that a number of separate driver may be fromthe driving pulley.

8. Belt drive: Utility.

Belt drive is commonly used for transmission of power when exact velocityratio is not required. Generally, belt drives are used to transmit power fromone pulley to another, when the two pulleys are not more than 10 metersapart.

9. What are the types of ropes?The types of ropes are:Fiber ropes.

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Wire ropes.

10. What is a Quarter turn left drive.?The quarter turn left drive is used with shafts arranged at right angles androtating in one definite direction.

11. Define the velocity ratio of the belt drive.The velocity ratio of the belt drive is defined as the ratio between thevelocities of the driver and the follower or the driven.

12. What are the Advantages of V-belt?

(i) Power transmitted is more due to wedging action in the groovedpulleys.

(ii) V-belt is more compact, quite and shock absorbing.

(iii) The V-belt drive is positive because of negligible slip between thebelt and the groove.

(iv) High velocity ratio may be obtained.

13. What are the Disadvantages of V-belt.?(i)It cannot be used with large center distances.

(ii)It is not as durable as flat belt.(iii)It is a costlier system.

14. What are Circular belts or ropes.?(i)Ropes are circular in cross section.(ii)It is used to transmit more power.(iii)Distance between two pulleys is more than 8metres.

15. What are the different Belt materials.?Flat belts :Leather, canvas, cotton & rubber.V-belts: Rubberized fabric & rubber.

Ropes :Cotton, hemp & manila.

16. Name the types of friction.Static friction.Dynamic friction.

17. Define the angle of repose.

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TWO MARKS Q&A


UNIT-V-FRICTION

If the angle of inclination of the plane to horizontal lis such that the bodybegin to move down the plane the angle is called the angle of repose.

18. What is meant by frictional force?Force of friction is always acting in the direction opposite to the direction ofmotion.

19. Why self locking screws have lesser efficiency?Self locking needs some friction on the thread surface of the screw andhence it needs higher effort to lift a body and hence automatically theefficiency decreases.

20. What is static friction?

It is the friction experienced by a body, when at rest.

21. What is dynamic friction?It is the friction experienced by the body, when in motion. The dynamicfriction is also called as kinematic friction.

22. What is co-efficient of friction?It is defined as the ratio of the limiting friction(F) to the normal reaction(RN)between the two bodies It is generally dented by

= F/RN

.23. Define screw jack.

The screw jack is the device used to lift the heavy loads by applying acomparatively small effort at its handle. The working principle of screw

jack is similar to that of an inclined plane.

24. What are difference between Square thread vs V-thread.?V-thread is stronger and often moves frictional to the motion than squarethreads.

A given load may be lifted by applying lesser force by square thread ascompared to V-threads.

V-threads are capable of taking more loads as compared to squarethreads.

25. What is the effort required to lift a 50tonne lorry using screw jack?( =0.3 =20)Q = tan_

= tan(0.3)= 16.64

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TWO MARKS Q&A


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W = 50tonne

= 50*10*9.81= 490.5KN

Effort required to lift the lorry P=Wtan(+Q)= 490.5 tan(16.69+20)= 365.59KN.

26. What is an Open belt drive.The open belt drive is used with shaft arranged parallel and rotating insame direction. The tension in the lower side will be more than in the

upper side belt because of more tension in the lower side belt, the lowerside belt is known as tight side where as the upper side is known as theslack side.

27. What is Open belt drive with one idler pulley.Idler pulleys are provide to obtain high velocity ratio and when the requiredbelt tension cannot be obtained by other means. Idler pulley is alsoknown as jockey pulley.

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