Motion

                 Class 9 

                            Physics 

                                    Chapter 1 

                Motion

     What is motion?

           THE MOVEMENT OF A BODY (OR OBJECT) IS CALLED MOTION.

Distance            

·       ➧When a body move from one point to another point the distance travelled refer to     the actual length of the in direct path.

·      ➧    It is scalar quantity.

·     ➧It travelled has only magnitude.

Displacement

·           ➧Displacement refer to the straight line path between the initial and the final           position.

·          ➧Displacement has magnitude  as well as direction.

·         ➧  It is vector quantity .

Uniform motion

·          ➧  A body has uniform motion  if it travels equal distance in a equal interval of time .

·           ➧The distance time graph for uniform motion is a straight line.

Non-uniform motion

·        ➧   A body has non- uniform motion  if it travels unequal distance in a equal interval     of time .

·       ➧   Motion of a freely falling body is an example of non-uniform motion.

·        ➧  The distance time graph for non-uniform motion is a curved line.

·        ➧  Non-uniform motion is also called acceleration.

Speed

·           ➧Speed of a body the distance travelled by it per unit time.

·          ➧Speed=distance/time.

·          ➧The si unit of the speed is m/s.

·         ➧  Speed is a scalar quantity.

·         ➧  Speed has no direction.

Velocity

·          ➧Velocity of a body is the distance travelled by it per unit time in a given direction.

·            ➧Velocity=displacement (s)/time taken(t).

·         ➧ The si unit of the velocity is m/s.

·        ➧   It  Is Vector quantity.

·         ➧   It has specific direction.

·          ➧The direction  of velocity is the same as the  direction of displacement  of the body .

Speed and velocity are not equal in magnitude

·         ➧The magnitude of the speed and velocity of a moving body is equal only if the     body moves in a single straight line.

·       ➧   If a body does not body moves in a single straight line. Then  Speed and velocity are not equal.

Acceleration

·          ➧  Acceleration  of  a body ids defined as the rate of change of its velocity with time.

·           ➧Acceleration=change in velocity(final velocity-  initial velocity) /time.

·           ➧Si unit is meter/second square.

Uniform Acceleration

·           ➧A body has a Uniform Acceleration if its velocity changes at a uniform rate.

Non-Uniform Acceleration

·           ➧A body has a non-Uniform Acceleration if its velocity changes at a non-uniform rate.

Average velocity

·         ➧Av.  velocity  =  u + v/2.        {u=initial   ,  v= final velocity}

Equations of uniformly accelerated motion

1.  v= u + at .

2. s=ut + 1/2at².                {s= distance }

3.v²=u² +2as.                      {a= acceleration}

Note .

I    ➺  If a body start from rest , its initial velocity , u=0

(    ➺ If a body comes to rest , its final velocity, v=0

(     ➺If a body moves with uniform velocity, its acceleration, a=0

Uniform circular motion        →

·          ➧When a body moves in a circle, it is called circular motion.

·           ➧When a body moves along a circular path, then its direction of the motion keeps   changing continuously.

·           ➧The force which is needed to make an object travel  in a circular path is called     centripetal force.         →