CBSE Class 11-science Answered

What does negative slope of a position -time graph actually represent? I mean that it does indicate motion in the opposite direction, but does it also represent the fact that the velocity of the object is decreasing? Also, shouldn't graphs representing motion in an opposite direction start from the origin and move below the x-axis, but I have seen in many graphs that the graph for motion in opposite direction starts from a point above the x-axis?

Please help me clear this doubt regarding negative slopes of graphs.

Asked by kumar.ashlesha | 09 May, 2016, 10:02: PM

Expert Answer

Negative Position-Time Graph with respect to Velocity

In position and time graphs, the slope of line indicates the velocity.
Therefore negative slope of a position-time graph actually indicates negative velocity.
Negative velocity is defined as the velocity of the object moving in an opposite direction.
Negative slope i.e in this case negative velocity does not mean that the velocity is decreasing.
Graph of negative velocity need not move below the x-axis.
The following are the few examples of a negative slope of a position -time graph.

The above image shows a negative slope i.e negative velocity in a position-time graph.

The graph goes gradually downward indicating the slow rate of negative velocity.

The above image also shows a negative slope of position-time graph.
But as the negative slope is comparitively more than that of previous graph, we conclude the rate of negative velocity is fast.

Similar is the concept for negative slope of a position -time graph in terms of acceleration

Answered by Abhijeet Mishra | 27 Nov, 2017, 03:06: PM