Important Short Questions and Answers: Friction in the Machine Elements

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 machines obviously 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 it approaches the pulley lie in a plane perpendicular to the axis of that pulley or must lie in the plane of the pulley, otherwise the belt will run off the pulley.

7. What is the use of rope drive?

 The rope drives are widely used when large power is to be transmitted continuously from one pulley to another over a considerable distance. One advantage of rope drives is that a number of separate driver may be from the driving pulley.

8. What is the use of belt drive?

 Belt drive is commonly used for transmission of power when exact velocity ratio is not required. Generally, belt drives are used to transmit power from one pulley to another, when the two pulleys are not more than 10 meters apart.

9. What are the types of ropes?

 The types of ropes are: *Fiber ropes. *Wire ropes.

10. What is the use of quarter turn left drive?

The quarter turn left drive is used with shafts arranged at right angles and rotating 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 the velocities of the driver and the follower or the driven.

12. What are the advantages of V-belt?

*Power transmitted is more due to wedging action in the grooved pulleys. *V-belt is more compact, quite and shock absorbing.

*The V-belt drive is positive because of negligible slip between the belt and the groove. *High velocity ratio may be obtained.

13. What are the disadvantages of V-belt?

*It cannot be used with large center distances.

*It is not as durable as flat belt.

*It is a costlier system.

14. What is the use of circular belts or ropes?

*Ropes are circular in cross section.

*It is used to transmit more power.

*Distance between two pulleys is more than 8metres.

15. Specify the various belt materials.

16. Name the types of friction.       

*Static friction.    

*Dynamic friction.

17. Define the angle of repose.

If the angle of inclination ‘α’ of the plane to horizontal is such that the body begin to move down the plane. Then the angle α 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 of motion.

19. Why self locking screws have lesser efficiency?

Self locking needs some friction on the thread surface of the screw and hence it needs

higher effort to lift a body and hence automatically the efficiency 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 dynamic friction 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 denoted by μ.     μ=F/RN.

23. Define screw jack.

The screw jack is the device used to lift the heavy loads by applying a comparatively small effort at its handle. The working principle of screw jack is similar to that of an inclined plane.