Velocity

Speed:

“The time rate of change of distance of a body is called speed”. Speed is a scalar quantity.

Unit:

Its unit is meter. (m/s).

Velocity:

“The rate of change of displacement is called velocity”. It is a vector quantity and its direction is along the direction of displacement.

Unit:

The SI unit of velocity is meter per second and its dimensions is [LT-¹].

Average velocity:

“The ratio between the total displacement and the total time taken by the body is called average velocity”.

Example:

A squash ball come back to its straight point after bounching off the wall a number of times. Its total displacement is zero so its average velocity is also zero.

Instantaneous velocity:

“The velocity of the body at instant of time, or at any point of its path with the limit that time intervel tends to zero”.

The limiting value of ∆d/∆t as the limit interval ∆t approaches zero.

Explanation:

Consider a body moving along a path ABC in the xy plane as shown in adjacent figure. At any time t, let the body be at point A. Its position is given by position vector r1. After a short interval of time ∆t the body reaches at point B which is given by the position vector r2.

The displacement of the body during this short interval of time is given by

The instantaneous velocity at point A can be found by making the time interval ∆t smaller and smaller. Then the displacement ∆d will become smaller and smaller and ultimately approaches A.

Thus the velocity at a particular position along the whole path can be found. During this time term ∆d/∆t does not completely to zero. Direction of instantaneous velocity at A is along the tangent at A.

The average velocity of the body may be zero even though its instantaneous velocity is not zero.

Uniform velocity:

“If the instantaneous velocity does not change body is said to be moving with uniform velocity”.

Variable velocity:

“If the instantaneous velocity changes, then body is said to be moving with variable velocity”.< View more on psalmfresh.blogspot.com for more educating and tricks article Thank you