Statics of Particles Interview Questions and Answers:

1. Define Force.

Ans. Force is an external energy which is applied on the body to change the state of rest or state of uniform motion.

2. Define resultant of a force.

Ans. It is a single force which produces the same effect as that of the force system. It is an equivalent force of all the given forces.

3. Distinguish between coplanar forces and concurrent forces.

Ans.

If line of action of all forces lie on a single plane then the system of forces are called coplanar forces.
In concurrent force system the line of action of all forces pass through a single point.

4. Distinguish between collinear forces and parallel forces.

Ans.

If line of action of all forces pass through a single line then the system of forces are called collinear forces.
In parallel force system the line of action of all forces are parallel to each other.

5. Define composition of forces.

Ans. The process of determining the resultant force of a force system is called composition of forces or compounding of forces.

6. What are the different methods of finding resultant force?

Ans.

1. Analytical method

• Trigonometric method
• Resolution method

2. Graphical method

7. State triangle law of forces.

Ans. It states, “If two forces acting on a body arc represented by the sides of a triangle in order, then their resultant is represented by the third side of the triangle taken in the opposite order.

8. State Polygon law of forces.

Ans. It states, “If any number of forces are represented in magnitude and direction by the sides of a polygon, taken in order, their resultant is represented by the closing side of the polygon taken in opposite order.

9. Define Resolution of force.

Ans. It is the process of splitting up the given force into number of components.

10. Define the term ‘Equilibrant’.

Ans. The single force which brings the force system to equilibrium is called as an equilibrant.

11. Distinguish between ‘Equilibrant’ and ‘Resultant’.

Ans. The equilibrant is equal and opposite to the resultant of force system.

12. Define Moment.

Ans. The product of magnitude of a force and the perpendicular distance of the line of action of the force from a point is known as moment of the force about that point.

13. Define the term ‘Moment centre’.

Ans. The point about which the moment is determined is called as moment centre.

14. Differentiate the effect of force and moment on a body.

Ans. The force applying on body will cause linear displacement while the moment will cause angular displacement.

15. What are the different types of moment?

Ans.

• Clockwise moment
• Anticlockwise moment

16. Differentiate between clockwise moment and anticlockwise moment.

Ans. In clockwise moment, the moment turns or rotates the body in clockwise direction, but in anticlockwise moment, the moment turns or rotates the body in anticlockwise direction.

17. When a system (in different orientation) is said to be an equivalent force system?

Ans. When the resultant forces are equal in magnitude, direction and hence the system is said to be an equivalent force system.

18. Define the term ‘Wrench’.

Ans. When the resultant of a force system is a couple vector parallel to a resultant force, then the type of resultant is said to be a wrench.

19. What are the types of wrench?

Ans.

• Positive wrench
• Negative wrench

20. State the principle of transmissibility of forces.

Ans. It states, ” the state of a body is unaltered if a force acting on the body is replaced by another force of same magnitude and direction acting anywhere along the line of action of the force”.

21. What is the limitation of transmissibility of forces?

Ans. It is used to determine the external forces not the internal forces in the body.

22. State Varignon’s theorem of moments.

Ans. It states, ” In a coplanar force system, the moment of the resultant of the forces about any point is equal to the algebraic sum of the moment of all the forces about the same point.

23. Define the term Couple.

Ans. A couple is formed by a pair of equal and opposite forces which are separated by certain distance.

24. What do you mean by ‘ arm of a couple’?

Ans. The perpendicular distance between the line of action of the two unlike equal parallel force is known as arm of couple.

25. When will be two couples are said equivalent?

Ans. Any two couples whose magnitude of moments are equal and of the same sign are said to be equivalent.

26. What is meant by coplanar concurrent force system?

Ans. In a force system, if the line of action of forces are lying on a single plane and all forces passing through a single point then the force system is called coplanar concurrent force system.

27. How will you revolve a given force into a force and couple?

Ans. The force system is unaltered by applying the same force in upward and downward directions on the same body at some distance. By this way we can revolve a given force into a force and a couple.

28. What is the difference between external forces and internal forces?

Ans.

External forces: The forces which represent the action of other bodies on the rigid body considered and which are responsible for the external behavior of the rigid body are called as ‘External forces’.
Internal forces: The forces which hold together the particles forming the rigid body or holding the component parts together are called as ‘Internal forces’.

29. Define moment of a couple.

Ans. The product of one of the forces of the couple and arm of the couple is known as moment of the couple.

30. What is the difference between moment and a couple?

Ans. The couple is a pure turning effect which may be moved anywhere in its own plane, or into a parallel plane without change of its effect on the body, but the moment of a force must include a description of the reference axis about which the moment is taken.