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.