Uniform Motion occurs when an object travels at a constant speed, covering equal distances in equal intervals of time.
Non-Uniform Motion describes objects that accelerate or decelerate, meaning their speed changes throughout the duration of the movement.
The Average Speed provides a single value representing the entire journey, calculated by dividing the total distance by the total time taken.
Instantaneous Speed refers to the exact speed of an object at a specific moment in time, which may differ significantly from the average speed.
Manual Measurement: This involves using a ruler or tape measure for distance and a stopwatch for time; it is simple but prone to human reaction time errors.
Trundle Wheels: For long distances, such as measuring a track or a field, a trundle wheel is used to count rotations and calculate distance accurately.
Light Gates: These digital sensors provide high precision by timing how long an infrared beam is obstructed by a moving object.
Single Light Gate Method: A 'flag' of known length passes through the gate; the timer measures the duration the beam is blocked, and speed is calculated as .
Double Light Gate Method: Two gates are placed at a known distance apart; the timer records the interval between the object breaking the first beam and the second beam.
On a Distance-Time Graph, the y-axis represents the distance from a starting point and the x-axis represents the elapsed time.
The Gradient (slope) of the line on a distance-time graph is numerically equal to the speed of the object.
A straight diagonal line indicates constant speed, while a horizontal line indicates the object is stationary (speed = 0).
A curved line indicates changing speed; a steeper curve represents acceleration, while a flattening curve represents deceleration.
| Feature | Manual (Stopwatch) | Automated (Light Gates) |
|---|---|---|
| Precision | Low (limited by human reaction) | High (millisecond accuracy) |
| Best Use | Slow objects, long distances | Fast objects, laboratory experiments |
| Setup | Simple, requires minimal gear | Requires sensors and data loggers |
| Error Source | Reaction time, parallax error | Alignment of sensors, flag length accuracy |
Check Units: Always ensure distance is in metres and time is in seconds before calculating speed in m/s; convert km to m (x) and minutes to seconds (x).
Formula Rearrangement: Use the formula triangle to correctly derive or depending on what the question asks for.
Gradient Calculation: When finding speed from a graph, choose two points far apart on the line to minimize percentage uncertainty in your gradient calculation.
Experimental Descriptions: If asked to describe an experiment, explicitly name the equipment (e.g., 'metre rule' instead of 'ruler') and state the specific equation used.
