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Home » Class 9 » Motion » Acceleration

Acceleration

Last Updated on April 21, 2020 By Mrs Shilpi Nagpal 2 Comments

Question 1 What is meant by the term acceleration?

Question 2 State the S.I. unit of acceleration?

Question 3 Define the term uniform acceleration.Give one example?

Question 4 Define the term non-uniform acceleration.Give one example?

Question 5 What is the acceleration of a body moving with uniform velocity?

Question 6 What type of motion is exhibited by freely falling body?

Question 7 What is retardation?

Acceleration
It is defined as rate of change of velocity with time.

                          Change in velocity
Acceleration =  ——————————–
                               Time taken for change

 

                   = Final velocity – Initial velocity
                    —————————————
                             Time taken for change
                          v-u
                  a = ——
                           t
S.I. unit is m/s2 or cm/s2.

Acceleration is a vector quantity.

If a body moves with uniform velocity its acceleration will be zero because its velocity is zero.

Uniform acceleration

A body has a uniform acceleration if it travels in a straight line and its velocity increases by equal amount in equal intervals of time.

For Ex:Motion of freely falling body, bicycle going down the slope, ball rolling down in inclined plane.

Non-uniform acceleration

A body has a non-uniform acceleration if its velocity increases by unequal amount in equal intervals of time.

For Ex:Car running on a crowded city road(At one moment its velocity increases and at other velocity decreases.)

Retardation/Deceleration/Negative acceleration
Acceleration can be
1)Negative(velocity decreases):Acceleration
2)Positive(velocity increases):Deceleration
A body is said to be retarded if its velocity decreases.
For Ex: A train is retarded when it slow down on reaching station because its velocity decreases.
Retardation is indicated by negative sign.It means velocity of body is decreasing.

                             v+u
Average velocity = ——-
                               2

Filed Under: Class 9, Motion Tagged With: acceleration, deceleration, negative acceleration, Non-uniform acceleration, retardation, uniform acceleration, vector quantity

About Mrs Shilpi Nagpal

Author of this website, Mrs Shilpi Nagpal is MSc (Hons, Chemistry) and BSc (Hons, Chemistry) from Delhi University, B.Ed (I. P. University) and has many years of experience in teaching. She has started this educational website with the mindset of spreading Free Education to everyone.

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Comments

  1. jose says

    April 4, 2020 at 9:13 pm

    good work madam… its very useful, but i think upgrdation of topics are required

    Reply
  2. Pradyumna Tadas says

    July 3, 2020 at 9:34 am

    Thank you so much.

    Reply

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