New
New
Year 10
OCR
Higher

Measuring instantaneous speed analysis (v=s/t)

I can accurately measure the instantaneous speed of a dynamics trolley and analyse patterns in its behaviour.

New
New
Year 10
OCR
Higher

Measuring instantaneous speed analysis (v=s/t)

I can accurately measure the instantaneous speed of a dynamics trolley and analyse patterns in its behaviour.

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Lesson details

Key learning points

1. A dynamics trolley speeds up (accelerates) along the whole length of a steep ramp.
2. Instantaneous speed is the average speed over a very short time period.
3. Taking measurements by reading the timing lines at eye level improves accuracy.
4. 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.

Shallow angles of ramp are needed to produce measurable times. Trying to draw lines of best fit can be challenging for pupils, as they will assume a straight line. Model how to identify and draw curved lines to them.
Teacher tip

Content guidance

• Equipment requiring safe usage.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Starter quiz

6 Questions

Q1.
Match the units to the quantity they measure.

metres

seconds

kilograms

metres per second

Q2.
How is average speed calculated?
$$\text{average speed} = \text{distance} \times \text{time}$$
$$\text{average speed} = \text{distance} + \text{time}$$
Correct answer: $$\text {average speed} = {\text{distance} \over \text{time}}$$
$$\text{average speed} = \text{distance} – \text{time}$$
$$\text{average speed} = \text{distance} \times \text{time}^2$$
Q3.
Match the symbol to the quantity.
Correct Answer:$$s$$,distance (displacement)

distance (displacement)

Correct Answer:$$v$$,speed (velocity)

speed (velocity)

Correct Answer:$$t$$,time

time

Q4.
Why is the instantaneous speed of a trolley greater at the bottom of the ramp than near the top?
Correct answer: 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.
Q5.
During an experiment, a trolley rolls down a ramp, getting faster as it moves. Which two statements are correct?
The instantaneous speed is constant.
Correct answer: The instantaneous speed is greatest at the bottom of the ramp.
The instantaneous speed is greatest at the top of the ramp.
Correct answer: The greatest instantaneous speed is higher than the average speed.
The greatest instantaneous speed is lower than the average speed.
Q6.
Calculate the speed of a trolley if it travels a distance of 10 cm in 0.2 s. Give your answer in m/s.
Correct Answer: 0.5 m/s, 0.5, 0.5 metres per second, 50 cm/s

Exit quiz

6 Questions

Q1.
Match the key word or phrase to the explanation.
Correct Answer:repeatable,when the same results can be achieved by the same person and method

when the same results can be achieved by the same person and method

Correct Answer:reproducible,when the same results can be achieved by a different person or method

when the same results can be achieved by a different person or method

Correct Answer:instantaneous speed,the speed at a particular moment in time

the speed at a particular moment in time

Correct Answer:direct proportional,when one variable is a constant multiple of the other

when one variable is a constant multiple of the other

Q2.
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.
Correct answer: Have another person follow the same method and compare their results with yours.
Compare you final answers with values from a textbook.
Q3.
Which of these should be included in a good written method?
Correct answer: A clear set of instructions that will allow valid data to be collected.
Correct answer: A description of how the control variables will be controlled.
A complete set of results.
Correct answer: A suitable range for the independent variable.
A graph of the results.
Q4.
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
Correct answer: The line of best fit is straight.
The gradient of the line is zero (flat).
Correct answer: The line of best fit passes through the origin (0,0).
The line of best fit is vertical (goes straight up).
Q5.
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.
Correct answer: Draw a single curved line that passes through, or close to, the points.
Draw a series of curves through the points.
Q6.
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.
Correct answer: The time is very short so would produce a very large error in the speed.
It is hard to measure 5 cm accurately.
Correct answer: It will not be possible to start and stop the watch accurately.
The distance is too large to estimate instantaneous speed over.