Motion in One Dimension-
Before you go through this article, make sure that you have gone through the previous article on Motion in One Dimension.
We have discussed-
- In one-dimensional motion, particle moves along a straight line.
- It is also known as rectilinear motion.
Various parameters related to motion are-
In this article, we will discuss about distance and displacement.
|Distance is the total length of the actual path travelled by a particle during its motion.|
- A particle moves in a circular path of radius R.
- It starts its journey from point A and ends at the same point.
Distance covered by the particle during its motion
= Circumference of the circle
= 2πR units
The characteristics of distance are-
- It depends upon the path followed by the particle.
- It is a scalar quantity.
- Distance is always positive. It can never be negative.
- Distance can not decrease with time.
- Distance is never zero for a moving particle.
- The SI unit of distance is meter (m).
- The dimensional formula of distance is [M0L1T0].
|Displacement is a vector drawn from the initial position to the final position of the particle.
Its magnitude is equal to the shortest distance between the initial and final position.
Mathematically, it is equal to the change in position vector of the particle.
- A particle is initially at point A having position vector .
- The particle moves to point B having position vector .
- A particle moves along a straight line from point O to point A.
- It then travels back from point A to point B as shown-
Magnitude of displacement of the particle
= Shortest distance between its initial and final position
= 70 m – 0 m
= 70 m
Direction of displacement is towards +ve X-axis.
It is important to note that here the distance covered by the particle = 100 m + 30 m = 130 m.
The characteristics of displacement are-
- It is independent of the path followed by the particle.
- It is a vector quantity.
- Displacement can be positive, negative or zero.
- Displacement can decrease with time.
- Displacement may be zero for a moving particle.
- The SI unit of displacement is meter (m).
- The dimensional formula of displacement is [M0L1T0].
Difference Between Distance And Displacement-
Some important differences between distance and displacement are-
|It is the total length of the actual path travelled by a particle during its motion.||It is the shortest distance between the initial and final positions.|
|It depends upon the path followed by the particle.||It is independent of the path followed by the particle.|
|It is a scalar quantity.||It is a vector quantity.|
|Distance is either positive or zero. It can never be negative.||Displacement can be positive, negative or zero.|
|Distance can never decrease with time.||Displacement may decrease with time.|
|Distance between a given set of initial and final position can have infinite values.||Displacement between a given set of initial and final position is unique.|
|Distance is never zero for a moving particle.||Displacement may be zero for a moving particle.|
It is important to note the following points-
- Magnitude of displacement can never be greater than distance.
- Magnitude of displacement is equal to the distance if the particle moves along a straight line without changing the direction.
When a particle returns to its initial position,
- Its displacement is always zero.
- Its distance covered is not zero.
According to convention,
- If the particle moves upwards or towards right, its displacement is taken positive.
- If the particle moves downwards or towards left, its displacement is taken negative.
To gain better understanding about Distance and Displacement,
Next Article- Problems On Distance & Displacement
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