1.  Particle Assumption  Modeling of Problem  Free Body Diagram: FBD  Newton’s Law of Motion  1 st Law  2 nd Law  3 rd Law Chap.#3: Statics of Particles

2. Particle Assumption: The size and shape of object are negligible. –Thus, mass of particle concentrate at a point. Note All forces acting on object are concurrent forces. That is, All forces act at a point. W T N

3. Problem Solving Strategy: Physical Model: –Transformation of actual problem into simpler one Assumptions –Using Free Body Diagram: FBD Mathematical Model: –Newton’s Law: F=0 and M o =0 (Select coordinate System) Set of equations to be solved Solution of Equations: –Computational Tools: Maple, Matlab, Prog. Conclusions: Does answer make sense?

4. Law #1: Body is in Equilibrium Body will remain at rest or continue to move with same speed (accel.=0) and direction unless an unbalanced force is acted on body or particle. Newton’s Laws of Motion

5. Newton’s Law of Motion Law #2: Non-equilibrium Change of motion of a body is proportional to the next force imposed on the body and is in direction of net force. For Equilibrium it is required that,

6. Newton’s Law of Motion Law #3: Action & Reaction If one body exerts a force on a second body, then second body exerts a force on the first body that is equal in magnitude, opposite in direction and collinear (same line of action).

7. Definition of Free-Body Diagram A free-body diagram is a sketch of an object or connected group of objects, modeled as a single particle, that isolates the body from its environment or surrounding bodies and represents the interaction of its environment by external forces.

8. Drawing a Free-Body Diagram Step 1: Imagine particle “FREE” from surroundings. –Draw sketch of external boundary of body. Step 2: Indicate all forces, known & unknown –If direction of force is unknown then assumed a direction. –Magnitude of a force is always positive, if answer is negative, the minus sign indicates that sense is opposite to the assumed earlier. Step 3: For each FBD Newton’s Laws of equilibrium must be used.

9. Example 1: Tension Cables Determine the tension in cords AB & AD for equilibrium of the 10Kg block. B AD C

10. Example 2: Determine the tension in cables A & B for equilibrium if traffic light weights 200lb B A

11. Example 3: Normal Force Prob. (3.3) find the normal forces at points NA and NB. The weight of cylinder is W=500lb. Show the FBD and steps. y x A B

12. Example 4: Problem 3.2: Block A rest on a smooth (frictionless) surface. If the mass of the block is 100Kg, determine the force exerted on the block by the surface and the force P required to prevent the motion of the block. yx P 8 3