Solution: Free Body Diagram of Point C: W = 2.8 kN C T1 = 5 kN T2 = 5 kN 1.2 m Ans.: ACB = 1.25 mĩ Problem 2.2 (Beer Johnston_10th edition_P2.53)Ī sailor is being rescued using a boatswain’s chair that is suspended from a pulley that can roll freely on the support cable ACB and is pulled at a constant speed by cable CD. Determine the shortest chain sling ACB that can be used to lift the loaded bin if the tension in the chain is not to exceed 5 kN. Free Body Diagram is specially necessary in problem where a particle is in equilibrium condition.Ĩ Problem 2.2 (Beer Johnston_10th edition_P2.62)Ī movable bin and its contents have a combined weight of 2.8 kN. Resolve the components of the force or use triangle rule to find out two equations for the two unknown force. Steps: Draw a Free Body Diagram of the most significant point, here it is P. we need to determine the tension in the individual rope. We need to know whether the ropes can carry the load or not i.e. Suppose 75 kg crate equivalent to 736 N weight is to be lifted using rope-pulleys. The three forces will be in equilibrium if and only if R = ∑F = 0 ∑Fx = ∑Fy = 0 Remember Newton If the resultant force acting on a particle is zero, the particle will remain at rest (if originally at rest) or will move with constant speed in a straight line (if originally in motion).ħ Forces in a Plane Forces on a Particle Free Body Diagram of a Particle Resolution of Forces into Components Rectangular Components Unit Vectors F = Fxi + FyjĪddition of Forces Using its Components Resolving into ComponentsĦ Forces in a Plane Forces on a Particle Equilibrium of a Particle Resultant of Multiple Forces Addition of Vectors Triangle Rule Parallelogram Law Polygon Rule Resultant of Concurrent Forces Introduction to Statics Partha Kumar Das Lecturer Department of Mechanical Engineering, BUETĢ Statics of Particle Forces in a Plane (2D Analysis)įorces in a Space (3D Analysis) Statics of Particleģ Forces in a Plane Forces on a Particle Point Force Vector If the number of restraints exceeds the number of degrees of freedom, the body is in equilibrium but you will need techniques we won't cover in statics to determine the reactions.Presentation on theme: "ME 245 Engineering Mechanics and Theory of Machines Portion 2"- Presentation transcript:ġ ME 245 Engineering Mechanics and Theory of Machines Portion 2 If the restraints correctly interpreted, then equal constraints and degrees of freedom create a stable system, and the values of the reaction forces and moments can be determined using equilibrium equations. Stability is highly desirable for reasons of human safety, and bodies are often restrained by redundant restraints so that if one were to fail, the body would still remain stable. If a degree of freedom is not restrained, the body is in an unstable state, free to move in one or more ways. Three-dimensional rigid body have six degrees of freedom - three translations and three rotations.įor a body to be in static equilibrium, all possible movements of the body need to be adequately restrained.
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