--- title: "Scope and importance of applied mechanics; FBD" subject: "Applied Mechanics" chapter: 1 key: "semester_1/applied_mechanics:scope-importance-applied-mechanics-fbd" source: https://www.bctengineer.com/q/semester_1/applied_mechanics/scope-importance-applied-mechanics-fbd site: BCT Engineering --- # Scope and importance of applied mechanics; FBD Applied Mechanics · Chapter 1: Introduction - Asked in: 2070 Chaitra, 2+2 marks - Video: [INTRODUCTION TO APPLIED MECHANICS|CHAPTER FIRST|INTRODUCTION|नेपालीमा|MECHANICS|TU|PU|KU|PoU|CTEVT](https://www.youtube.com/watch?v=XMIgO4hBMuw) — Engineering Dreams - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_1/applied_mechanics/scope-importance-applied-mechanics-fbd - Whole chapter: https://www.bctengineer.com/md/semester_1/applied_mechanics/chapter-1 ## Question Describe the scope and importance of applied mechanics in engineering study. Define free body diagram with examples. ## Short answer Applied mechanics is fundamental to engineering, providing the laws for analyzing forces in structures and machines, ensuring safe design, and forming the basis for strength of materials and dynamics. A free body diagram is a sketch of an isolated body showing all external forces and moments; e.g., a ladder against a wall shows its weight, wall reaction, ground normal force and friction. ## Answer #### Scope and importance of applied mechanics - It supplies the laws (equilibrium, Newton's laws, friction, motion) used to analyse every engineered object, so it is the base of civil, mechanical, electrical and computer engineering studies. - In design it gives the forces in beams, trusses, frames and machine parts, so members can be made safe and economical. - It explains the motion of vehicles, projectiles and machines, and the effect of friction. - Subjects such as strength of materials, structural analysis, machine design and fluid mechanics depend on it. - It develops the habit of modelling a real problem, applying principles and checking the result. #### Free body diagram A **free body diagram (FBD)** is a sketch of a body, or a part of a structure, isolated from its surroundings, showing all the external forces and moments acting on it, including the support reactions and its own weight. It is drawn by separating the body, replacing every support or contact with the force it exerts, and adding the applied loads and weight. **Example 1: ladder against a smooth wall.** The ladder AB (weight W at its middle) leans on a wall at A and rests on the ground at B. ```text |A | \ N_A (horizontal, away from wall) wall | \ | o W (down, at mid-point) | \ -----+--------\B--- ground N_B (up), F (friction, towards wall) ``` **Example 2: a block on an inclined plane.** The FBD shows the weight W acting down, the normal reaction N perpendicular to the plane and the friction force F along the plane. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. A free body diagram shows: A. Only the internal forces of the body B. Only the applied loads, with supports left in place C. The deformed shape of the body D. The body isolated from its surroundings with all external forces and moments Answer: D. An FBD isolates the body and shows all external forces, moments, reactions and weight. (Key point: FBD definition) 2. When drawing an FBD, each support or contact is: A. Drawn as a wall B. Replaced by the force it exerts C. Replaced by the body's mass D. Ignored Answer: B. Supports are removed and replaced by the reactions they produce. (Key point: Drawing an FBD) 3. For a ladder on the ground at B against a smooth wall, the forces at B are: A. Normal reaction upward and friction along the ground B. Friction along the ground only C. Weight only D. A horizontal wall force only Answer: A. The ground gives N_B up and friction F horizontally. (Key point: Ladder FBD) 4. In the FBD of a block on an incline, the normal reaction N acts: A. Along the plane B. Vertically upward always C. Down the slope D. Perpendicular to the plane Answer: D. Normal reaction is perpendicular to the contact surface; friction acts along the plane. 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