According to selina discuss non-uniform velocity and instantaneous velocity (class 9)
Answers
Hi!!!
Variable velocity: A body is said to be moving with variable velocity if its average velocity is different between different points along its path either in magnitude or in direction or both in magnitude as well as direction.
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A body is said to be moving with variable velocity if it covers distances in unequal intervals of time or unequal distances in equal intervals of time, however small these intervals may be, or it changes its direction of motion.
Instantaneous velocity: When a body is moving with variable velocity, then its velocity at a particular instant of time or at a particular point along its path is known as its instantaneous velocity. It is equal to the limiting value of average velocity as dt tends to zero.
Instantaneous velocity is equal to the differential coefficient of displacement w.r.t time.
The velocity of a body can be variable either due to change in its magnitude or in its direction or in both. IF A BODY MOVES UNEQUAL DISTANCES IN A PARTICULAR DIRECTION IN EQUAL INTERVALS OF TIME OR IT MOVES EQUAL DISTANCES IN EQUAL INTERVALS OF TIME BUT ITS DIRECTION OF MOTION DOES NOT REMAIN THE SAME, THEN THE VELOCITY OF THE BODY IS SAID TO BE VARIABLE (or,non-uniform).
For a body moving with variable velocity,the velocity of the body at any instant is called its instantaneous velocity. It is important to have time interval small enough so that the direction of motion does not change during this interval.
ILLUSTRATED PICTURE : The picture attached at the top of this answer shows you the circular path of constant speed but variable velocity (since in a circular path, the direction of motion of a body continuously changes).
USEFUL FACT : During the circular motion, at any instant,its velocity is along the tangent to the circular path at that point as shown in the topmost illustrated picture.
