Measuring speed accurately
Lesson details
Learning outcome
I can clearly describe how to measure speed and explain how I can do this accurately.
Key learning points
- The instantaneous speed of an object is the speed at a particular moment in time.
- For an accurate measurement a person needs to be in line with the observation.
- Manual timing can lead to a range of timing errors.
- Repeat readings can reduce the effect of random errors.
- Some readings are anomalous and these should not be used in caluations of averages.
Keywords
Average speed - The average speed of an object is the distance it travels per unit of time, measured in metres per second (m/s). It is a scalar quantity.
Instantaneous speed - The instantaneous speed of an object is its speed at a particular moment.
Timing error - Manual timings include some timing errors. These can be due to reaction times or observing from incorrect positions.
Random error - Random errors are errors that vary from test to test in an uncontrolled way.
Common misconception
Pupils commonly confuse instantaneous and average speeds.
Be very careful when using the word speed, always use 'average' or 'instantaneous' explicitly, linking average speed to a time period.
Teacher tip
Modelling movement with a motion sensor will really help show the difference between average and instantaneous speed. Move from one end of the room to the other while stating your instantaneous speed and then have pupils calculate average speed.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Match the units to the quantities they are used to measure.
distance
time
speed
Q2.Which of these equations shows how distance travelled can be calculated from average speed and time?
Q3.Starting with the slowest, sort these objects in order of speed.
Q4.A student measures how long a trolley takes to fall a distance of 1.5 m three separate times. Their readings are 2.5 s , 2.1 s, and 2.0 s. Calculate the average roll time.
Q5.A trolley was allowed to roll along a series of tracks of different steepness giving different average speeds. Starting with the slowest, sort the results in order of increasing average speed.
Q6.A toy car rolls through a distance of 3.2 m in a time of 1.6 s. Calculate the average speed of the trolley giving the correct unit.
Assessment exit quiz
6 Questions
Q1.Match the key words to the explanations.
unpredictable difference between measurement and true value
a difference in a measurement of time and the true time
the speed at a particular moment
overall distance travelled divided by overall time taken
Q2.Select the reading that has a large timing error in this set of timing data.
Q3.Five different trolleys are rolled along a 3.0 m track. Their times are shown. Starting with the fastest, put them into order of speed.
Q4.Which of these will help to reduce timing errors in a trolley rolling experiment?
Q5.Due to a timing error a student measures a time that is longer than the true time. How will this affect the speed they calculate for a rolling trolley?
Q6.Suggest which of the following items would be the most accurate way of measuring the time taken for a ball to be thrown across the lab?
To help you plan your 8 science lesson on: Measuring speed accurately, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 8 science lesson on: Measuring speed accurately, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 3 science lessons from the Moving by force unit, dive into the full secondary science curriculum, or learn more about lesson planning.