Factors affecting ball bounce
This level 4-5 teaching activity focuses on what makes a fair test when carrying out a science investigation.
About this resource
The combination of the material properties of a ball (surface textures, actual materials, amount of air, hardness or softness, and so on) affects the height of its bounce. The complexity of this investigation encourages students to begin to think critically about the design and results of the investigation.
Factors affecting ball bounce
Levels: 4–5
Nature of science achievement aims: Understanding about science, investigating in science
Contextual strands: Material world
Topic: Sports studies
Matauranga Māori
Due to the geographical isolation of New Zealand, early Māori settlers had little contact with neighbouring islands. Trade and commerce were internally based, so there was no need for a precise measuring system. However, activities such as wharenui construction, waka making, woodcarving, navigation, and weaving did require a high degree of precision. This precision came from the skill, experience, and eye of the operator rather than by reference to a defined standard.
Read more here Science Learning Hub Pokapū Akoranga Pūtaiao: Early Māori measurement.
Learning activity
- A variety of balls could be grouped according to one or more of their properties, for example:
- table tennis ball, golf ball, squash ball, solid rubber ball (similar sizes)
- solid rubber balls in different sizes (similar materials)
- old and new tennis balls (different surface textures and ages).
- A measuring stick or ruler marked in centimetres is long enough to record the highest ball bounce.
- A similar length stick is marked in 5–10 cm bands of colour.
- What makes a ball bouncy? Collect a range of ideas from the students.
- How can you tell which factor (for example, size, material, surface texture, age) is most important in making the ball bouncy? How could you test this?
- How would you make sure your method could be repeated under the same conditions?
- What measurements would you take to gather your data?
- Encourage students to rank a series of balls based on what they think is important, and prepare to test them in that order. For example, if they think size is important, they might prepare to test balls of similar materials, ranging from small to large.
- Could the same ball act differently in different conditions?
Note: In this situation, no single fair test will give a conclusive result (which is typical of scientific work); even though students may do their best to design a fair test, it will not be possible to isolate the material variables of each ball, which combine to make it bouncy.
Note: This activity may pose difficulties with stopping the ball at the moment of its greatest bounce height and dealing with parallax. Using a camera and/or a banded ruler can help overcome these problems.
1. Get the students to develop a fair test to compare the height of bounce for each ball using the first measuring stick or ruler.
2. Have them list all the variables they think will affect ball bounce. (Their ideas might include surface texture, colour, size, what it’s made of, squashiness, opacity, weight, air pockets, temperature, cost, shininess or dullness, hardness or softness, age, and layers of materials.)
3. Get them to share their ideas on which variables they can test, which they cannot test, and why.
4. Have them take turns:
- dropping each ball from an agreed height
- determining the maximum height of the bounce.
5. Have them record their results.
6. Discuss any variation in measurements and get the students to suggest what the possible variables might be. For example, you could ask:
- What are the variables around dropping the ball?
- What are the variables involved in determining the height of the bounce? (For example, deciding when the ball is at its height.)
- Does the height of the person making the reading have any effect on the reading itself? (For example, do taller students consistently take a different reading compared with shorter students?) If so, why?
7. Use this line of questioning to lead to a discussion on parallax (an apparent displacement of an object, for example, a ball), with respect to a more distant background (for example, a measuring stick, when viewed from two different positions).
8. Get students to repeat the measuring exercise using the colour-banded stick and record where, within the bands, each type of ball bounces.
9. Focus the students on the aim of the experiment (that is, to determine a pattern from which to make comparisons rather than to gather specific measurements) and discuss:
- Which is the better method for this activity?
- Why might one method be chosen over the other in different circumstances?
- How much data do you need to collect before you can develop some degree of certainty to make a statement about the patterns in your data?
- What pattern(s) did your tests show? How did the pattern(s) compare with what you expected?
- How relevant do you think your data is? How certain are you about its accuracy?
- How could you improve the accuracy of the information you have collected?
- When you were setting up the fair tests, how did you decide what to test?
- On the basis of the fair tests you carried out, what seem to be the material properties of bounciness? What other tests might you need to do to check these assumptions?
- Can you isolate the most important property that determines the ball's height?
- Do you think you have carried out even one fair test? Is it a fair test if you can’t account for all the variables in a ball?