Review Questions

REVIEW QUESTIONS

1. Define friction. Explain with examples, whether friction is friend or foe to human.

2. Briefly describe the various types of friction experienced by a body.

3. Differentiate between sliding and rolling friction with suitable examples.

4. Define the terms limiting angle of friction and angle of repose. Explain how they are related.

5. Prove or disprove the following statement: "Angle of friction is equal to angle of repose".

6. Prove that the angle of friction is equal to the angle made by an inclined plane with the horizontal when a solid body, placed on the inclined plane, is about to slide down.

 [A.U., Nov/Dec 2009]

 [Hint: Refer Section 6.2.5]

7. Derive an expression for the least force required to drag a body on a rough horizontal plane.

8. Derive an expression for minimum force required to slide down on a rough inclined plane.

9. Derive an expression for the effort to be applied on a body for moving it down the rough inclined plane when (1) effort applied is horizontal, (ii) effort applied is parallel to the plane. Also derive an expression for the efficiency of the inclined plane.

10. Show that the maximum efficiency of a square threaded screw moving in a nut is where ϕ is the angle of friction.

11. Derive the condition for maximum efficiency of screw.

12. Explain the principle of working of a screw jack and derive an expression for its mechanical advantage.

13. Derive from first principles an expression for the effort required to raise a load with a screw jack taking friction into consideration.

14. Determine the equation to determine the torque required to lift the load by a screw jack. 

15. What do you mean by overhauling and self-locking screws?

16. Why square threads are preferred to V-threads for lifting loads?

17. Derive the frictional torque developed in flat pivot bearing under uniform pressure condition. 

[A.U., Apr/May 2011]

[Hint: Refer Section 6.12]