What is Mechanics?Mechanics is a branch ofscience which deals with bodies at rest or motion under the action of forces.
Structure of Mechanics Mechanics Applied Mechanics (Mechanics applied to Engg. Problem) Mechanics of Rigid Bodies Mechanics of Deformable (Things that do not change Bodies Mechanics of Fluids shape) (Things that do change shape)Statics Dynamics Incompressible Compressible Kinetics Kinematics(Forces which causes the (Forces which causes the motion motion are considered) are not considered)
Fundamental ConceptsParticle- it is an idealized body which may have negligiblemass and whose size and shape can be neglectedMatter- substances that posses weight, occupies space,volume, apprehended by sense.Body: the matter bounded by a closed surface is calledbody. It is accumulation of large number of particlesRigid Body- if the relative distance between the particle ofthe body is same before and after the application of forces.Deformable body: if the relative distance between theparticle of the body is different(change) before and after theapplication of forces.
Space - associated with the notion of the position of a point Pgiven in terms of three coordinates measured from a referencepoint or origin. ORThe unlimited expanse of physical dimensions in which allmaterial objects are locatedTime- It is a measure of duration between successive events.Force - Represents the action of one body on another.A force is characterized by its point of application, magnitude,and direction.In Newtonian Mechanics, space, time, and mass are absolute concepts,independent of each other. Force, however, is not independent of the otherthree. The force acting on a body is related to the mass of the body andthe variation of its velocity with time.
Systems of UnitFPS: Foot, Pound, SecondCGS: Centimeter, Gram, and SecondMKS: Metre, Kilogram and secondSI: System International
Fundamental Units Physical Unit Symbol Unit Quantity symbol length l metre m mass m kilogram kg time t second selectric current I ampere Athermodynamic T kelvin K temperature amount of n mole mol substance
Prefix of SI systemSr. Prefix Symbol ExpontialNo. Notation1 Exa E 10182 Peta P 10153 Tera T 10124 Giga G 1095 Mega M 1066 Kilo K 1037 Hecto h 1028 Deka da 1019 Deci d 10-110 Centi c 10-212 Milli m 10-313 Micro 10-614 Nano n 10-915 pico p 10-12
Derived Units Physical Unit Unit Symbol QuantityAcceleration metre/second2 m/s2Angular Velocity radian/second rad/sAngular radian/second2 rad/s2accelerationForce Newton N or kgm/s2Moment of Force Newton metre NmWork, Energy Joule J or NmTorque Newton metre NmPower Watt W= J/s2Pressure Pascal Pa = N/m2Frequency Hertz Hz or 1/s
Fundamental PrinciplesNewton’s First Law: If the resultant force on a particle is zero, theparticle will remain at rest or continue to move in a straight line.
• Newton’s Second Law: A particle will have an acceleration proportional to a nonzero resultant applied force.• When a force acts on an object, the object accelerates in the direction of the force.• If the mass of an object is held constant, increasing force will increase acceleration.• If the force on an object remains constant, increasing mass will decrease acceleration.
Newton’s Third Law: The forces of action and reactionbetween two particles have the same magnitude and line ofaction with opposite sense.
Newton’s Law of Gravitation: Two particles are attracted withequal and opposite forces.•every point mass in the universeattracts every other point mass with aforce that is directly proportional tothe product of their masses andinversely proportional to the square ofthe distance between them. GM W = mg g = G = 6.67 x 10-11 Nm2/kg2 R2
Law of Parallelogram of Forces If the two forces acting at a point be represented in magnitude and direction by the two adjacent sides of a parallelogram, then their resultant is represented in magnitude and direction by the diagonal of the parallelogram passing through that point. The magnitude of Resultant force R• Parallelogram Law
Law of Triangle of forces“If the forces acting at a point be representedin magnitude and direction by the three sidesof a triangle taken in order, they will be inequilibrium.”
Lami’s Theorem: if three forces acting at a fixed pointare in equilibrium, each force will beproportional to the sine of the anglebetween the other two forces.”
Principle of TransmissibilityConditions of equilibrium or motion are not affected bytransmitting a force along its line of action. F and F’ are equivalent forces.
TaskDraw one simple mechanism to liftthe body or water or weight.Make the group of five students.