Starter quiz
- Match the units to the quantity they measure.
- metres⇔distance ✓
- time⇔seconds ✓
- mass⇔kilogram ✓
- speed⇔metres per second ✓
- How is average speed calculated?
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- Match the symbol to the quantity.
- ⇔distance ✓
- ⇔speed ✓
- ⇔time ✓
- Why is the instantaneous speed of a trolley greater at the bottom of the ramp than near the top?
- A resultant force is acting on the trolley, causing it to speed up. ✓
- Frictional forces are increasing the speed of the trolley.
- The trolley is producing more energy as it moves faster.
- The mass of the trolley is decreasing as it travels.
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- During an experiment, a trolley rolls down a ramp, getting faster as it moves. Which two statements are correct?
- The instantaneous speed is constant.
- The instantaneous speed is greatest at the bottom of the ramp. ✓
- The instantaneous speed is greatest at the top of the ramp.
- The greatest instantaneous speed is higher than the average speed. ✓
- The greatest instantaneous speed is lower than the average speed.
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- Calculate the speed of a trolley if it travels a distance of 10 cm in 0.2 s. Give your answer in m/s.
- '0.5 m/s' ✓
Exit quiz
- Match the key word or phrase to the explanation.
- repeatable⇔when the same results can be achieved by the same person and method ✓
- reproducible⇔when the same results can be achieved by a different person or method ✓
- instantaneous speed⇔the speed at a particular moment in time ✓
- direct proportional⇔when one variable is a constant multiple of the other ✓
- How can you check that a practical result is reproducible?
- plot a graph to see if there is a relationship between variables
- collect another set of results to compare with the first
- have another person follow the method and compare their results with yours ✓
- compare your final answers with values from a textbook
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- Which of these should be included in a good written method.
- a clear set of instructions that will allow valid data to be collected ✓
- a description of how the control variables will be controlled ✓
- a complete set of results
- a suitable range for the independent variable ✓
- a graph of the results
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- A pupil produces a graph to see if there is a relationship between two variables. What features would the graph have if the variables are directly proportional to each other?
- the line of best fit is curved
- the line of best fit is straight ✓
- the gradient of the line is zero (flat)
- the line of best fit passes through the origin (0,0) ✓
- the line of best fit is vertical (goes straight up)
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- A pupil produces a graph to see if there is a relationship between two variables. The points do not seem to follow a straight line. How should they draw a line of best fit?
- repeat the experiment until they get results that will give a straight line
- join the points with a series of straight lines, like a dot-to-dot
- draw a single straight line from the origin to the last point plotted
- draw a single curved line that passes through, or close to, the points ✓
- draw a series of curves through the points
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- A pupil suggests measuring the time it takes a trolley to roll 5 cm down a ramp using a stopwatch to get an accurate value of instantaneous speed. Why is this unlikely to produce an accurate result?
- the time is very short so would produce a very small error in the speed
- the time is very short so would produce a very large error in the speed ✓
- it is hard to measure 5 cm accurately
- it will not be possible to start and stop the watch accurately ✓
- the distance is too large to estimate instantaneous speed over
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- A dynamics trolley speeds up (accelerates) along the whole length of a steep ramp.
- Instantaneous speed is the average speed over a very short time period.
- Instantaneous speed is the average speed over a very short time period.
- Repeated readings by different observers helps to check for systematic errors.
Common misconception
It is important for the same person to take all the measurements.
Emphasise that if the method is a good one then everyone carrying it out carefully should get similar results that show the same pattern (the results are repeatable and reproducible).
Keywords
Repeatable - A measurement is repeatable if the same (or similar) results are obtained when the same person repeats the investigation using the same method.
Reproducible - A measurement is reproducible if the same (or similar) results are obtained when the same person repeats it using a different method, or a different person repeats it using the same method.
Instantaneous speed - The instantaneous speed of an object is its speed at a particular moment in time.
Directly proportional - If two variables are directly proportional, when one variable increases, the other increases at the same rate.