Summary
Highlights
For the entire 12-second journey, the total distance traveled is 12 meters. The average speed for the whole journey is 12 meters / 12 seconds = 1 m/s.
A distance-time graph illustrates an object's movement over time. A straight line indicates constant speed, with a steeper gradient signifying higher speed. A flat horizontal line means the object is stationary.
The speed of an object can be calculated by finding the gradient of the line using the formula: speed = distance / time. If distance is in meters and time in seconds, speed is in meters/second.
To find the instantaneous speed at a specific point on a curved graph (e.g., at 9 seconds), draw a tangent to the curve at that point. Then, form a right-angled triangle using the tangent to measure distance and time, and calculate speed (distance / time). This method is often for higher-tier exams only.
The video provides practice questions. It then reviews a graph, identifying acceleration (upwards curve at 'A'), steady speed (straight line at 'B'), stationary (horizontal line at 'C'), and deceleration (decreasing gradient at 'D').
For the first 8 seconds, the distance traveled is 4 meters. The average speed is 4 meters / 8 seconds = 0.5 m/s.
To find the speed at 11 seconds, draw a tangent. If the tangent covers 1 meter distance in 2 seconds, the speed is 1 meter / 2 seconds = 0.5 m/s. Note that due to varying tangent lengths, answers might slightly differ but should yield similar speeds.
When speed is not constant, the distance-time graph will have curves. An upward curve shows acceleration, while a curve that levels off indicates deceleration.
A journey can be broken down into segments: walking, stopping, and then walking again at different speeds. For example, 6m in 4s, then stopped for 3s, then 1m in 3s, then 5m in 2s.
To calculate the average speed between 0 and 4 seconds, find the distance traveled at 4 seconds (6 meters). Speed is then 6 meters / 4 seconds = 1.5 m/s.