## Saturday, February 4, 2017

### Motion in a Straight line Introduction and Average Velocity Video Lesson

Motion in a straight line an introduction

Studying the motion of the body without bothering about the forces acting on it is done in kinematics. We treat body as a combination of identical point sized objects and they have negligible dimensions. All laws of mechanics were in principle discussed with the point sized particles and as the body is the combination of similar particles, under ideal conditions the laws are applicable to bodies also. Here we are dealing with bodies moving with a velocity much lesser than the velocity of the light. In this particular case, body is moving only along one dimension either along X,Y or Z axis. This is called one dimensional motion and it is changing its position with respect to time and surroundings.

To measure the change of the position, we have terms like distance, speed. Distance is the actual path traveled by a body and the speed is the rate of change of distance with respect to time. Both distance and speed are treated as scalars and they can be understood by stating their magnitude alone and they don’t need direction.

Displacement is the shortest distance between initial and final positions in specified direction and it is treated as vector quantity. They can be understood completely only when both magnitude and directions are given to us. Velocity is defined as the rate of change of displacement and it is also a vector quantity.

Average velocity

If a particle is not changing its velocity with respect to time, then it is said to be in uniform velocity. In this case at any given interval of time, the particle will have same constant velocity and it is same every where. But it is not same every where. If a body is changing its velocity with respect to time, then it is having acceleration and we would like to measure the average velocity in the given case. Average velocity is defined as the ratio of total displacement covered by a body in the total time. Taking this concept into consideration, we can find average velocity when time is shared and displacement is shared as shown in the video below.

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