Area Under Velocity-Time Graphs (OCR GCSE Combined Science A (Gateway): Physics): Revision Note

Exam code: J250

Ashika

Written by: Ashika

Reviewed by: Caroline Carroll

Updated on

Area Under Velocity-Time Graphs

Higher Tier Only

  • The area under a velocity-time graph represents the displacement (or distance travelled) by an object

Velocity–time graph showing distance equals the area beneath the graph: an initial triangle labelled “one half times base times height” followed by a rectangle labelled “base times height”; axes are velocity and time.
The displacement, or distance travelled, is represented by the area beneath the graph
  • If the area beneath the graph forms a triangle (e.g. the object is accelerating uniformly from rest or decelerating uniformly to rest), then the area can be determined by using the following formula:

Area = ½ × Base × Height

  • If the area beneath the graph forms a rectangle (i.e. the object is moving at a constant velocity), then the area can be determined by using the following formula:

Area = Base × Height

Determining distance from a velocity-time graph

  • Enclosed areas under velocity-time graphs represent total displacement (or total distance travelled)

Velocity–time graph showing three enclosed areas beneath a line: Area 1 is an accelerating triangle, Area 2 a constant-velocity rectangle, and Area 3 a decelerating triangle.
Three enclosed areas (two triangles and one rectangle) under this velocity-time graph represents the total distance travelled
  • If an object moves with constant acceleration, its velocity-time graph will comprise straight lines

    • In this case, calculate the distance travelled by working out the area of enclosed rectangles and triangles as in the image above

Worked Example

The velocity-time graph below shows a car journey which lasts for 160 seconds.

Velocity–time graph of a car journey: velocity rises from 0 to 17.5 metres per second by 40 seconds, stays constant to 70 seconds, rises to 25 by 90 seconds, then falls to 0 at 160 seconds.

Calculate the total distance travelled by the car on this journey.

Answer:

Step 1: Recall that the area under a velocity-time graph represents the distance travelled

  • In order to calculate the total distance travelled, the total area underneath the line must be determined

Step 2: Identify each enclosed area

  • In this example, there are five enclosed areas under the line

  • These can be labelled as areas 1, 2, 3, 4 and 5, as shown in the image below:

Annotated velocity–time graph identifying five areas: triangle Area 1 from 0–40 seconds, rectangle Area 2 from 40–70 seconds, split Areas 3 and 4 from 70–90 seconds, and triangle Area 5 from 90–160 seconds; velocity reaches 25 metres per second.

Step 3: Calculate the area of each enclosed shape under the line

  • Area 1 = area of a triangle = ½ × base × height = ½ × 40 × 17.5 = 350 m

  • Area 2 = area of a rectangle = base × height = 30 × 17.5 = 525 m

  • Area 3 = area of a triangle = ½ × base × height = ½ × 20 × 7.5 = 75 m

  • Area 4 = area of a rectangle = base × height = 20 × 17.5 = 350 m

  • Area 5 = area of a triangle = ½ × base × height = ½ × 70 × 25 = 875 m

Step 4: Calculate the total distance travelled by finding the total area under the line

  • Add up each of the five areas enclosed:

total distance = 350 + 525 + 75 + 350 + 875

total distance = 2175 m

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Ashika

Author: Ashika

Expertise: Physics Content Creator

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.

Caroline Carroll

Reviewer: Caroline Carroll

Expertise: Head of Content Delivery

Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about delivering high-quality resources to help students achieve their full potential.