Graphical Representation makes it simpler for us to understand data. When analyzing motion, graphs representing values of various parameters of motion make it simpler to solve problems. Let us understand the concept of motion and the other entities related to it using the graphical method.
Graphical Representation of Motion
Using a graph for a pictorial representation of two sets of data is called a graphical representation of data. One entity is represented on the x-axis of the graph while the other is represented on the y-axis. Out of the two entities, one is a dependent set of variables while the other is independent an independent set of variables.
We use line graphs to describe the motion of an object. This graph shows the dependency of a physical quantity speed or distance on another quantity, for example, time.
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Distance Time Graph
The distance-time graph determines the change in the position of the object. The speed of the object as well can be determined using the line graph. Here the time lies on the x-axis while the distance on the y-axis. Remember, the line graph of uniform motion is always a straight line.
Why? Because as the definition goes, uniform motion is when an object covers the equal amount of distance at equal intervals of time. Hence the straight line. While the graph of a non-uniform motion is a curved graph.
Velocity and Time Graph
A velocity-time graph is also a straight line. Here the time is on the x-axis while the velocity is on the y-axis. The product of time and velocity gives the displacement of an object moving at a uniform speed. The velocity of time and graph of a velocity that changes uniformly is a straight line. We can use this graph to calculate the acceleration of the object.
Acceleration=(Change in velocity)/time
For calculating acceleration draw a perpendicular on the x-axis from the graph point as shown in the figure. Here the acceleration will be equal to the slope of the velocity-time graph. Distance travelled will be equal to the area of the triangle, Therefore,
Distance traveled= (Base × Height)/2
Just like in the distance-time graph, when the velocity is non-uniform the velocity-time graph is a curved line.
Solved Examples for You
Question: The graph shows position as a function of time for an object moving along a straight line. During which time(s) is the object at rest?
- 0.5 seconds
- From 1 to 2 seconds
- 2.5 seconds
- I only
- II only
- III only
Solution: Option B. Slope of the curve under the position-time graph gives the instantaneous velocity of the object. The slope of the curve is zero only in the time interval 1 < t < 2 s. Thus the object is at rest (or velocity is zero) only from 1 to 2 s. Hence option B is correct.