An object is said to be in non-uniform motion if it undergoes equal displacements in unequal intervals of time, howsoever small these intervals may be.
Clearly,in non-uniform motion,the velocity of the object is different at different instants.
For example,when we run or travel in a vehicle from one position to another,we start from the condition of rest.We gain speed for some time and then may travel with constant velocity for sometime and finally slow down and come to a stop.In such a case,the velocity of object is different instants and hence this motion is non-uniform motion.
In non-uniform motion,the velocity of object in different forms is explained below.
(i) Variable velocity: An object is said to be moving with a variable velocity,if either its speed or its direction of motion or both change with time.
(ii)Average velocity: For a given motions of an object,the average velocity is that uniform velocity with which the object will cover the same displacement in a given interval of time as it does with its actual variable velocity during the giving interval of time.
The average velocity of an object can be positive or negative depending on the sign of displacement.It is zero if the displacement is zero.
(iii)Instantaneous velocity:The average velocity of the object in motion tells us how fast an object has been moving over a given interval of time.But it does not tell,how fast the given object is moving at different instants of time during motion.For this,we define instantaneous velocity.
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