what are the major differences between distance-time graph and displacement- time graph?

Asked by  | 16th Aug, 2011, 07:21: PM

Expert Answer:

The major differences between distance-time graph and displacement- time graph is that a distance-time graph always increases and never drops down, while a displacement graph could.

When we consider the distance covered without the direction of movement then irrespective of direction of movement the distance travelled will keep on increasing as long as speed will be positive.  In this situation the graph of time (x-axis) versus distance covered (y-axis) will always rise. When the speed is 0, the graph will be parallel to x-axis.  Please not that speed can only be 0 or a positive number. Speed can never be negative.

Displacement refers to the change in position with reference to a fixed reference point. This means that depending of direction of motion and the position of the moving object relative to the reference point the displacement may increase or decrease. Accordingly the graph of displacement may rise or fall.

For example, when a ball is thrown up vertically, the displacement of the ball relative to the earth increases as it goes up. However under the influence of gravity the speed of ball reduces till it becomes 0. Then the ball starts accelerating in downward direction. This means the speed again increases and the ball continues to move but in downwards direction. As a result displacement with respect of earth reduces, although the total distance travelled by ball continues to increase. This means that graph of displacement of ball with respect to earth will be initially rising but with reduced slope till it becomes parallel to x-axis. Immediately after that, the displacement graph will start tapering downwards with increasing slope.

Answered by  | 16th Aug, 2011, 08:43: PM

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