Measuring Speed (Edexcel GCSE Physics)
Revision Note
Typical Speeds
The table below gives some typical speeds (in m/s) for various everyday scenarios
Typical Speeds Table
Note that typical speeds of a person walking, running or cycling depends on a variety of factors, such as:
Age
Terrain
Fitness
Distance
Similarly, typical speeds of transportation systems like cars or planes will depend on their:
Shape
Design
Cost
Purpose
Worked Example
A student claims that people typically walk at 6 m/s.
a) State whether or not you agree with this claim and explain your reasoning.
b) Suggest a factor that can affect the typical speeds of a person walking.
Answer:
Part (a)
The student’s claim is incorrect because 6 m/s is too fast
The typical speed that people walk at is about 1.5 m/s
Part (b)
Some factors that can affect the typical speeds of a person walking are:
The terrain might be wet, rocky or steep
The age of the person
The fitness of the person
The length of the walk or journey
Examiner Tips and Tricks
You may be asked to recall typical values of speed for a person walking, running or cycling, or comment on typical values of speed for different types of transportation system - so learn the values in this table and have an idea about how they compare to each other.
Measuring Speed
Speed is the distance travelled by an object every second
The simplest way to measure the speed of an object, is to time how long it takes to travel a known distance and use the equation:
Choosing Equipment
To ensure a result for speed is as accurate as possible, choose the appropriate equipment to measure the distance and time
Some simple equipment that can be used to measure distance travelled and time taken for objects like a tennis ball and plastic cone
To compare the average falling speed of a tennis ball to a plastic cone, for example:
A metre rule could be used to measure the distance they fall from
A timer could be used to measure how long they take to reach the ground
It would not be practical to use a metre rule to measure the length of an athletics track though
In this instance, a more appropriate piece of equipment would be a (long!) tape measure, or even better, a trundle wheel
A trundle wheel is ideal for measuring long distances
Using Lights Gates to Measure Time
Light gates are pieces of digital equipment that allow times to be measured more accurately
Light gates can be used to accurately time the motion of objects in a laboratory
A light gate can be used to start a timer when an object passes through it
A flag on top of the moving object blocks a beam of light as it passes through the light gate, triggering the timer to start
A second light gate (at some fixed distance away) can be used to stop the timer as the object passes through it
Single Light Gates to Measure Speed
A single light gate can also be used to measure the speed of an object as it passes through
Example of using a single light gate to measure speed
The timer measures how long the light gate is blocked for
The distance travelled is given by the length of the flag passing through the light gate
The two measurements for distance travelled and time taken can then be used in the equation for speed
Examiner Tips and Tricks
Whenever you’re asked to describe an experiment, if you need to use an equation to calculate something, write this down first. The quantities in the equation give you some hints about the variables you might need to measure.
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