Engineering mechanics: Principal of transmissibility of force

Principle of transmissibility of forces:

  According to principle of transmissibility, the condition of rigid body will remain unchanged if the point of application of a force acting on the rigid body is transmitted to act at any other point along its line of action.

>It holds good only when the magnitude, direction and line of action of force remain the same.

Engineering mechanics: Force, characteristics of force, effects of force

Force:

     A force is a push or pull which changes or tends to change the state of rest or uniform motion of the body.

                          Or

     the product of mass and acceleration of a body is called force.

                 i.e. F = ma

                        Or

    The rate of change of momentum is called force.

                    i.e. F = dp/dt

SI unit-

               Since-

                         F = ma

                            = Kg×m/s^2

                            = Kgms^-2

  The SI unit of force is kgms^-2 or Newton.

Unit force of one newton force:

     unit force or one newton force is that force which produces an acceleration of 1m/s^2 in a mass of 1 kg.

                            

Characteristics of force:

1. A force is a vector quantity as it has both magnitude as well as direction.
2. It can change the position of moving or a rest object.
3. It is very useful in our daily life in both from applied and resistive.

Effects of force:

1. It can change the shape or size of an object.
2. It can change the direction of an moving object.
3. It can change the speed of an moving object.
4. It can make a stationary object.
5. It can stop a moving object.

Engineering mechanics- System of units

System of units:

       there are only for System of units which are commonly used and universally recognised.

                (a)C.G.S system of units

                (b)F.P.S system of units

                (c)M.K.S system of units

                (d)S.I units

(a)C.G.S system of units-

        In this system, the units of length, mass and time are centimetre, gram and second respectively.

(b)F.P.S system of units-

        In this system, the units of length, mass and time are foot,pound and second respectively.

(c)M.K.S system of units-

        In this system, the units of length, mass and time are metre ,kilogram and second respectively.

(d)S.I units (international system of units)-

        The eleventh general conference of weights and measures has recommended a unified and systematically constituted system of fundamental and derived units for international use. This System of units are called SI unit. In the system seven base quantities have been  assigned proper and standard units-

Engineering mechanics- Units, Fundamental units, derived units

Unit:

   It is a standard quantity of the same kind chosen in order to measure physical quantity.

Fundamental units:

   The physical quantity which does not depend on any other quantity are called fundamental physical quantities.

                                the unit of fundamental quantity is called fundamental unit.

                              Or

   The units selected for measuring mass, length, and time are called fundamental units.

Note: the fundamental units are not definable in terms of other quantities. for this reason, they are called base or fundamental units.

Derived units:

   The units of physical quantities which can be expressed in terms of fundamental units.(mass, length and time) are called derived units.

        

    (a) The unit of velocity is a derived unit

      

                Velocity= displacement/time

                              = Length/time

                              = m/s

     (b) unit of acceleration is a derived unit

               Acceleration = velocity/time

                                      = Displacement/time^2

                                      = Length/time^2

                                      = m/s^2

Engineering mechanics

Physical quantity:

    A quantity which can be measured is called physical quantity.

                 It is of two types-

(a)Scaler quantity

(b) vector quantity

(a)Scaler quantity:

         The physical quantity having only magnitude is called scalar quantity.

    Examples- length,mass, time, distance, volume, density, temperature, speed etc.

(b) vector quantity:

           The physical quantity having both magnitude and direction is called vector quantity.

    Examples: force, displacement, velocity, acceleration, momentum, etc.

Difference between scalar and vector quantity:

        There are following difference between scalar and vector quantity-

Engineering mechanics

Difference between mass and weight:

        There are following difference between mass and weight-