Motion

 Motion


In physics,there are two states -

  •  Rest or Stationary
  • Motion
Rest state- 
                  Position is fixed.

Examples-

Tree
School






House

Electric Pole


Motion State-
                        An object is said to be in motion (or moving) when its position changes continuously with respect to a stationary object taken as reference point.
Motion is the phenomenon in which an object changes its position with respect to time.

Examples-

Flying Birds
Swimming Fishes










Uniform Motion-
                             When body travels equal distances in equal intervals of time.
                             The distance-time graph for uniform motion is a straight line.




Non-uniform motion (Accelerated motion)-
                                    When body travels unequal distances in equal intervals of time.
                                     The distance-time graph for non-uniform motion is a curved line.






Physical Quantities-
                                   All those quantities which can be measured.
Ex. -  Length,Mass,Temperature,Time,Force,Pressure,Work.

Physical quantities can be classified into two categories — scalar and vector.
  • A scalar quantity has only magnitude, but no direction.Examples: Length,Mass,Time,Temperature
  • Vector quantity has both magnitude and direction.Example: Force
System of Units -
                             Tools using which can measure physical quantities effectively.

Distance -
                  It is the actual length of the path by a moving body irrespective of the direction in which the body travels.
Distance is a scalar quantity.

Displacement -
                          When the body moves from one position to another,the shortest distance between the initial position and final position of the body along with direction is known as displacement.
Displacement is a vector quantity.





The distance travelled by a moving body can not be zero but the displacement of a moving body can be zero.




Here distance travelled (from A to A) = 3+4+5=12 m
Displacement (from A to A)=0











Here Displacement from A to A=0






Speed - 
  •  The speed of a body gives us an idea of how slow or fast that body is moving.
  • Speed of a body is the distance travelled by it per unit time.
  • Speed is a scalar quantity.               
                    Speed= Distance travelled/Time taken

                               v = s/t
                    where v = speed
                               s = distance travelled
                               t = time taken (to travel that distance)

The SI unit of speed is m/s

    Average speed = Total distance travelled/Total time taken

Uniform Speed (Constant Speed) - 
                                                        A body has a uniform speed if it travels equal distances in equal intervals of time.
  • Speedometer gives the speed of a car in km/h.
  • Odometer records the distance travelled by a car in km.

     Velocity - 
                     Velocity of a body is the displacement produced per unit time.
        
     Velocity = Displacement/Time taken    
The SI unit of velocity is m/s.

When velocity is changing at uniform rate then

      Average velocity = Initial velocity+Final velocity/2
v bar = u+v/2

 where v bar = average velocity
            u= initial velocity
             v= final velocity
            
Uniform velocity - 
                            A body has a uniform velocity if it travels in a specified direction in a straight line and moves over equal distances in equal intervals of time.
The velocity of a body can be changed in two ways:
  1. by changing the speed of the body.
  2. by keeping the speed constant but by changing the direction. 

                     




                          

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