Parameters of Motion-
The motion of a body may be described through the following parameters-
In this article, we will discuss about distance and displacement.
|It is the total length of the actual path traveled by a body between its initial and final positions.|
Characteristics of Distance-
- The SI unit of distance is meter (m).
- It has only magnitude and no direction. Hence, it is a scalar quantity.
- It can never be negative. It is always positive or zero.
|It is the shortest distance measured in the direction from initial position to the final position.|
Characteristics of Displacement-
- The SI unit of displacement is meter (m).
- It has both magnitude and direction. Hence, it is a vector quantity.
- It may be positive, negative or zero.
Example of Distance & Displacement-
Consider four cities A, B, C and D located as shown-
A salesman starts from city A, goes to city B, then to city C and then to city D. Then,
Distance traveled by the salesman
= Length of the actual path covered
= AB + BC + CD
= 20 km + 30 km + 20 km
= 70 km
Magnitude of displacement of the salesman
= Shortest distance between the initial and final position
= Shortest distance between city A and city D
= 30 km
- The distance traveled by a body is always greater than or equal to the magnitude of displacement.
- The distance and displacement are same when body moves along a straight line path without taking any turn.
The displacement of the body is always zero if it returns back to its initial position.
The displacement of a body is independent of the choice of the origin of the position coordinates.
Differences Between Distance & Displacement-
The following table shows the differences between distance and displacement-
|It is the total length of the actual path traveled by a body between its initial and final positions.||It is the shortest distance measured in the direction from initial position to the final position.|
|It is a scalar quantity.||It is a vector quantity.|
|The distance covered by a body depends on the path followed by the body.||The displacement covered by a body does not depend on the path followed by the body.|
|Distance can never decrease with time.||Displacement may decrease with time.|
|It can never be negative. It is always positive or zero.||It may be positive, negative or zero.|
|There is always a distance covered whenever there is a motion.||There may be no displacement even when the body has moved.
It is possible when body comes back to its initial position.
|It is always greater than or equal to the magnitude of displacement.||It is always less than or equal to the distance covered.|
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