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 can be estimated by measuring movement in a small time period.
Anomalous readings should be repeated and replaced or removed from sets of repeat readings.

Common misconception

When the trolley is released it speeds up quickly at the start and then rolls at a constant speed.

Show a video of an accelerating trolley in slow motion, identifying the distance travelled in successive equal intervals of time.

Keywords

Dynamics trolley - A dynamics trolley is a wheeled object used in experiments. It moves very smoothly over flat surfaces.
Average speed - The average speed is the total distance travelled divided by the total time for a journey.
Instantaneous speed - The instantaneous speed of an object is the speed at a particular moment in time.
Anomalous reading - An anomalous reading is a result which is significantly outside the pattern in a set of results.

Measuring short time periods is difficult. To give the students a better chance of measuring the times accurately, the trolley should be moving fairly slowly, this can be achieved by making sure the ramps are not too steep and using a 'small distance' of 20 cm.

Teacher tip

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).

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Starter quiz

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6 Questions

Q1.

Izzy rode her bike for 3 hours and travelled 45 kilometres. What was her average speed?

10 km/h

Correct answer: 15 km/h

20 km/h

25 km/h

Q2.

Lucas rides his bike for 4 hours with an average speed of 15 km/h. He travelled at a speed of 10 km/h for the first two hours. What speed must he have been travelling at for the last two hours?

10 km/h

between 10 km/h and 15 km/h

15 km/h

Correct answer: higher than 15 km/h

Q3.

Which of the graphs shows an object moving with increasing speed (accelerating)?

Correct Answer: An image in a quiz

Q4.

Andeep ran 20 metres in 5 seconds then slowed down and walked 5 metres in the next 5 seconds. What was his average speed for the first 5 seconds?

1 m/s

2.5 m/s

Correct answer: 4 m/s

5 m/s

Q5.

Andeep ran 20 metres in 5 seconds then slowed down and walked 5 metres in the next 5 seconds. What was his average speed for the whole 10 seconds?

1 m/s

Correct answer: 2.5 m/s

4 m/s

5 m/s

Q6.

Aisha cycles to school three days in a row. Her speeds are shown on the bar chart. What is her average speed for the journey to school?

2.0 m/s

Correct answer: 3.7 m/s

4.0 m/s

5.0 m/s

Exit quiz

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6 Questions

Q1.

Match the key words or phrases to their definitions.

Correct Answer:average speed,the total distance travelled divided by the time taken

the total distance travelled divided by the time taken

Correct Answer:instantaneous speed,the speed of an object at a particular moment

the speed of an object at a particular moment

Correct Answer:dynamics trolley,a wheeled object used in motion experiments

a wheeled object used in motion experiments

Correct Answer:anomalous reading,a result which does not fit the pattern of a set of results

a result which does not fit the pattern of a set of results

Q2.

Which of these statements about instantaneous and average speed is correct?

The instantaneous speed of an object is always less than the average speed.

The instantaneous speed of an object is always greater than the average speed.

The instantaneous speed of an object is always the same as the average speed.

Correct answer: The instantaneous speed of an object can change during a journey.

The instantaneous speed of an object is constant during any journey.

Q3.

A student investigates the relationship between the steepness of a ramp and the instantaneous speed of a trolley at the end of the ramp. Which of these are control variables for the investigation?

the speed of the trolley at the end of the ramp

the steepness of the ramp

Correct answer: the length of the ramp

Correct answer: the distance the speed is measured over

Correct answer: the mass of the trolley

Q4.

A trolley rolls down a ramp and passes between two markers that are 20 cm apart in a time of 0.25 s. Calculate the speed of the trolley in m/s.

Correct Answer: 0.8 m/s, 0.8, 0.80 m/s, 0.80, 80 cm/s

Q5.

A pupil collects the following set of timing data for a moving object: 0.25 s, 0.23 s, 0.35 s, 0.22 s, 0.21 s. Which calculation should the pupil use to find the mean time?

mean time = (0.25 + 0.23 + 0.35 + 0.22 + 0.21) ÷ 5

mean time = (0.25 + 0.23 + 0.22 + 0.21) ÷ 5

mean time = (0.25 + 0.23 + 0.35 + 0.22 + 0.21) ÷ 4

mean time = (0.25 + 0.23 + 0.35 + 0.22) ÷ 4

Correct answer: mean time = (0.25 + 0.23 + 0.22 + 0.21) ÷ 4

Q6.

A trolley rolls down a ramp passing between two markers, 0.20 m apart. The following results are collected: 0.17 s, 0.18 s, 0.17 s, and 0.20 s. Calculate the mean instantaneous speed for the trolley.

0.18 m/s

Correct answer: 1.1 m/s

1.0 m/s

0.35 m/s

0.28 m/s

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