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How to Find Displacement on a Position Time Graph

How to Find Displacement on a Position-Time Graph

The knowledge of how to find displacement on a position-time graph is very important for anyone studying physics or interested in understanding the motion of objects. Displacement refers to the change in an object’s position, and it’s an essential concept to comprehend in physics.

To find displacement on a position-time graph, you need to determine the difference in position (final position minus initial position) for the given time interval. It involves identifying the points on the graph corresponding to the initial and final times and then calculating the difference in their respective position values. Mathematically, it can be expressed as:

Displacement = Final Position – Initial Position

On the graph, the displacement is represented by the vertical distance between the corresponding points on the position-time axis. If the graph is a straight line, the displacement is simply the difference in the y-coordinates of the two points. If the graph is curved, you may need to use calculus to find the area under the curve, which represents the displacement.

How to Determine Displacement on a Position-Time Graph

The process of determining displacement on a position-time graph involves interpreting the graph’s shape and slope. Here’s how you can do it:

  1. Interpreting the Graph:
    To begin, carefully examine the position-time graph. The vertical axis represents the position, while the horizontal axis represents time. The graph’s shape can provide valuable insights into an object’s motion. An upward-sloping line indicates positive velocity, a downward-sloping line indicates negative velocity, and a horizontal line suggests the object is at rest.
  2. Calculating Displacement:
    Displacement is the change in position. It can be calculated by finding the difference between the initial and final positions of the object. This is often represented as Δx = x_final – x_initial, where Δx is the displacement, x_final is the final position, and x_initial is the initial position.
  3. Using Slope for Instantaneous Displacement:
    The slope of the position-time graph at a specific point represents the object’s instantaneous velocity. To find the instantaneous displacement at a particular time, determine the slope of the tangent line at that point. The steeper the slope, the greater the velocity and displacement.
  4. Understanding Positive and Negative Displacement:
    Positive displacement indicates that an object has moved in the positive direction (right), while negative displacement suggests movement in the negative direction (left). The magnitude of displacement is always positive, as it represents the absolute distance between the initial and final positions.
  5. Area Under the Graph:
    In cases of non-uniform motion, the area under the position-time graph between two time points represents the displacement. If the graph is above the time axis, the displacement is positive; if it’s below, the displacement is negative.
  6. Uniform Motion Scenarios:
    In scenarios of uniform motion, where velocity remains constant, finding displacement is straightforward. Multiply the constant velocity by the time interval to obtain displacement.

How to Find Displacement on a Position-Time Graph in Complex Scenarios

Sometimes, the motion isn’t as simple as uniform motion. Here’s how to tackle more complex scenarios:

  1. Non-Uniform Motion:
    In cases where velocity changes over time, calculate displacement by integrating the velocity function over the time interval. This involves finding the area under the velocity-time graph.
  2. Curved Graphs:
    When dealing with curved position-time graphs, divide the curve into small segments. Approximate each segment as a straight line and calculate the displacement for each segment. Sum up these segmental displacements to get the total displacement.
  3. Back-and-Forth Motion:
    If an object moves back and forth, the displacement is the total distance between the initial and final positions, regardless of direction. Consider each segment separately and sum their magnitudes.
  4. Negative Velocity with Positive Displacement:
    In cases where an object moves in the negative direction (left) but ends up with a positive displacement, it implies that the object initially overshot its final position and then moved backward.


Q: Can displacement be greater than distance traveled?
A: Yes, displacement accounts for the change in position, while distance traveled considers the entire path taken. Displacement can be smaller than or equal to the distance traveled but never greater.

Q: How is displacement different from distance?
A: Displacement is a vector quantity that considers the change in position between initial and final points, while distance is a scalar quantity that represents the total path length traveled.

Q: What if the position-time graph is a horizontal line?
A: A horizontal line on the graph indicates that the object is at rest. The displacement is zero.

Q: Can displacement be negative?
A: Yes, negative displacement indicates movement in the opposite direction of the positive axis (left on the horizontal axis).

Q: How do you calculate displacement from a velocity-time graph?
A: To find displacement from a velocity-time graph, calculate the area under the velocity-time curve within the given time interval.

Q: Is displacement the same as the magnitude of distance?
A: Yes, displacement’s magnitude is the same as the distance between the initial and final positions. However, displacement considers direction.

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What Does the Slope of a Position-Time Graph Represent?