Statics and Systems of Forces - One Line Questions

1. What is a free body diagram (FBD)? — A diagram showing all external forces acting on a body.
2. What is the transmissibility of force? — A force can be moved along its line of action without changing its effect on the rigidity of the body.
3. If two forces of equal magnitude and opposite direction act on a body, what is their resultant? — Zero force.
4. In the context of statics, what does the term 'friction' represent? — A force that opposes relative motion or impending motion between surfaces in contact.
5. For a system of forces acting on a plane, if the resultant force is zero, the system is equivalent to: — A couple.
6. What is the 'wrench' in the context of a system of forces? — A combination of a force and a couple acting along the same line.
7. What is a statically determinate structure? — A structure where internal forces can be determined solely by the equations of statics.
8. What is a statically indeterminate structure? — A structure where internal forces cannot be determined solely by the equations of statics.
9. In the principle of virtual work, for a system in equilibrium, the total virtual work done by all forces and moments is: — Zero.
10. Lami's theorem applies to a system of: — Three forces acting on a body in equilibrium.
11. If a system of forces is reducible to a single force R and a couple C, and R is non-zero, the system can be further reduced to a single force if: — The line of action of R is adjusted such that it passes through the point where the moment of C is balanced by the moment of R.
12. The angle of repose is equal to the: — Tangent of the coefficient of static friction
13. What is the algebraic sum of the resolved parts of a system of forces in equilibrium along any direction? — Zero.
14. If a force F is resolved into two components Fx and Fy along the x and y axes respectively, and the angle between F and the x-axis is θ, then Fx = ? — F cos θ
15. If a force F is resolved into two components Fx and Fy along the x and y axes respectively, and the angle between F and the x-axis is θ, then Fy = ? — F sin θ
16. The resolution of a force into components is: — Finding two or more forces that have the same effect as the original force.
17. What is the principle of moments? — For equilibrium, the sum of clockwise moments about any point is equal to the sum of anticlockwise moments about the same point.
18. What are concurrent forces? — Forces that act at the same point.
19. What are collinear forces? — Forces that act along the same line.
20. What are coplanar forces? — Forces that act in the same plane.
21. A beam supported at two points is subjected to a downward load in the middle. What are the reactions at the supports? — Forces that oppose the load and maintain equilibrium.
22. What is the parallelogram law of vector addition? — If two vectors are represented by adjacent sides of a parallelogram, their sum is represented by the diagonal passing through their common vertex.
23. What is the role of a centroid in statics? — It is the center of mass of a homogeneous body, and for a system of forces, it's related to the resultant.
24. What is the effect of a couple on a rigid body? — It produces a net moment but no net force.
25. What is the Lami's theorem? — It relates the forces acting on a body in equilibrium to the sines of the angles opposite to them.
26. Why is a free body diagram essential in solving statics problems? — It simplifies the visualization of forces and helps in applying equilibrium equations.
27. The unit of moment of a force in the SI system is: — Newton-meter (Nm)
28. In Lami's theorem, if P, Q, and R are three coplanar forces in equilibrium, and α, β, and γ are the angles opposite to them respectively, then: — P/sin α = Q/sin β = R/sin γ
29. What is the difference between static friction and kinetic friction? — Static friction is generally greater than kinetic friction.
30. What is the fundamental difference between statics and dynamics? — Statics deals with bodies at rest or in uniform motion, while dynamics deals with accelerated motion.
31. Which of the following is NOT a condition for equilibrium of a rigid body under a system of forces? — Sum of forces in z-direction = 0 (if 3D)
32. What is the angle of repose? — The angle at which an object begins to slide down an inclined plane.
33. What is the principle of superposition of forces? — The effect of a system of forces on a rigid body is the same as the effect of their resultant force.
34. What is the maximum static friction? — The friction force when the body is just about to move.
35. A body is in equilibrium if the sum of its components of forces along any two perpendicular axes are both zero. This is a consequence of: — The conditions for equilibrium.
36. What is the center of force? — The point of application of the resultant force.
37. What is the magnitude of the moment of a couple? — The product of one of the forces and the perpendicular distance between them.
38. What is the coefficient of static friction? — The ratio of the maximum static friction to the normal force.
39. What is the general condition for a system of forces to be equivalent to a single resultant force? — The resultant force is non-zero, and the resultant moment about a point on the line of action of the resultant force is zero.
40. What is the condition for a system of forces to be reducible to a single couple? — The resultant force is zero and the resultant moment about any point is non-zero.
41. Which condition must be met for a system of forces acting on a body to be in equilibrium? — Both the resultant force and the resultant moment about any point are zero.
42. What is the condition for a system of forces to be equivalent to a single force? — The resultant force is non-zero and the resultant moment about a point on the line of action of the resultant force is zero.
43. What is a resultant force? — The net effect of a system of forces, represented by a single force.
44. What is a moment of a force? — The tendency of a force to cause rotation about a point or axis.
45. What is the fundamental principle of statics regarding forces acting on a rigid body in equilibrium? — The vector sum of all forces is zero, and the sum of all moments about any point is zero.
46. Consider two forces acting on a point. If their resultant is zero, what can be said about the forces? — They are equal in magnitude and opposite in direction.
47. What is the purpose of using a virtual work method in statics? — To determine the equilibrium conditions by considering the work done by forces during a virtual displacement.
48. A couple consists of: — Two equal and parallel forces acting in opposite directions.
49. When is a system of forces reducible to a single force? — When all forces are coplanar and their resultant is non-zero.
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