One Dimensional 1-D Motion :: Horizontal, Vertical, Motion Direction

Learning Kinematics
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One Dimensional (1-D) Motion

As a first step to understanding kinematics, we study motion in one dimension. We try to understand the various aspects relating to motion using the motion of bodies executing translatory motion in one dimension.

One dimensional motion involves bodies moving along a straight line path. The one dimensional motion is further classified as :

• Motion along the Horiztonal
  This is one of the most common forms of motion that we study. The path traversed by the body is assumed to be horizontal and a horizontal coordinate line is assumed in relation to the path of the body.

  

• Motion along the Vertical
  This is another common form of motion that we study. The path traversed by the body is assumed to be vertical and a vertical coordinate line is assumed in relation to the path of the body.

  

• Oblique Motion
  A straight line which is neither vertical nor horizontal is Oblique. Motion along the Oblique line is the third case of 1-d motion which is out of the purview of our study at this level.

  

Direction of Motion

There are two directions that a body moving along a straight line path can take which are directed mutually opposite to each other. One of the directions is taken to be positive and the other negative. The coordinates representing the position of the body on the negative side are negative and on the positive side are positive.

Distance between two different locations of the body

One of the characteristics of a body executing translatory motion is that it changes its position. It moves from an initial location and may or may not reach the initial location at the end of the journey.

In kinematics we need to think of the distance covered by the body in moving from one position to another. This can be interpreted as the distance between two different locations of the body

The position of a body is described by its coordinate. The distance between two positions of the body is given by the difference between the coordinate of the final location and the coordiante of the initial location.

Distance = Coordinate of the Final Location − Coordinate of the Initial Location.

The sign of the result indicates the direction in which the body is moving.

For the Car moving along the horizontal, The left side is negative and The right side is positive.

For the rocket moving along the vertical, The upward direction is positive and The downward direction is negative.

The distance traveled by

The Car = (+ 5) − (− 1) = 5 + 1 = + 6

The Rocket = (+ 8) − (0) = 8 − 0 = + 8

The Car has moved a distance of 6 units from the initial location towards the negative side.
The Rocket has moved a distance of 8 units from the initial location towards the positive side.

Positive/Negative is a direction indicator

The positive and negative signs indicate the direction in which the body is located with respect to its original location.

Any one of the directions can be taken as positive and the other direction should be considered as negative. We can draw the same conclusions even if we interchange the directions.

The the origin of the coordinate system can also be anywhere. It is not a requirement that it should be at the initial location.

For the Car moving along the horizontal, The right side is negative and The left side is positive.

For the rocket moving along the vertical, The downward direction is positive and The upward direction is negative.

The distance traveled by

The Car = (+ 5) − (− 1) = 5 + 1 = + 6

The Rocket = (+ 8) − (0) = 8 − 0 = + 8

The Car has moved a distance of 6 units from the initial location towards the positive side.
The Rocket has moved a distance of 8 units from the initial location towards the negative side.

 

Author Credit : The Edifier

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