Speed-Time Graphs
Speed-time graphs, also known as velocity-time graphs, provide a visual representation of how an object’s speed changes over a specific period. These graphs are valuable tools for understanding the dynamics of motion.
Analysing a speed-time graph allows you to understand the motion of an object over time. It helps you identify periods of constant speed, acceleration, or deceleration. Steeper slopes indicate greater acceleration or deceleration.
Let’s explore the details of speed-time graphs:
Speed (Velocity) on the Y-Axis: The vertical axis of the graph represents the speed or velocity of the object. It is usually labelled in units such as metres per second (m/s) or miles per hour (mph).
Time on the X-Axis: The horizontal axis represents time, typically measured in seconds. Time increases as you move to the right on the graph.
Characteristics of Speed-Time Graphs:
Constant Speed: A horizontal line on the speed-time graph indicates that the object is moving at a constant speed. The slope of the line is zero because there is no change in speed over time.
Uniform Acceleration: A straight, diagonal line with a positive slope represents uniform acceleration. The steeper the slope, the greater the acceleration. This indicates that the object is speeding up at a constant rate.
Uniform Deceleration: A straight, diagonal line with a negative slope indicates uniform deceleration or slowing down. Again, the steeper the slope (in the negative direction), the greater the deceleration.
Curves and Changing Acceleration: Curved lines on the speed-time graph suggest changing acceleration. A curved line that is upward and getting steeper indicates acceleration increasing over time. Conversely, a downward-curving line getting less steep indicates deceleration.
Area Under the Graph: The area under the speed-time graph, between the graph and the time axis, represents the total distance travelled by the object. This is because distance is the product of speed and time ( Distance = Speed × Time ).
