NSW Syllabuses

# STEM Stage 2 – Activity 1

### Bouncing high

#### Description of activity

Students investigate balls made of different materials to determine whether the materials that make up the balls affect the way the balls bounce.

This activity could take up to three sessions:

• examine materials and plan the investigation
• carry out the investigation and gather data
• analyse the data and draw conclusions.

#### Context

Students recognise that different materials have different properties which determine their uses. They know how to gather data, record it and use tabulated data to construct a graph.

Students investigate a range of different materials used to make balls, identifying their properties.

With assistance, students devise methods to test and record how high a ball bounces. After gathering data, students can relate the properties of the materials used to make the balls to the ball’s ‘bounciness’.

#### Outcomes

Skills

ST2-4WS investigates their questions and predictions by analysing collected data, suggesting explanations for their findings, and communicating and reflecting on the processes undertaken
ST2-5WT applies a design process and uses a range of tools, equipment, materials and techniques to produce solutions that address specific design criteria
MA2-1WM uses appropriate terminology to describe, and symbols to represent, mathematical ideas
MA2-3WM checks the accuracy of a statement and explains the reasoning used

Knowledge and understanding

ST2-7PW describes everyday interactions between objects that result from contact and non-contact forces
ST2-13MW identifies the physical properties of natural and processed materials, and how these properties influence their use
MA2-9MG measures, records, compares and estimates lengths, distances and perimeters in metres, centimetres and millimetres, and measures, compares and records temperatures
MA2-18SP selects appropriate methods to collect data, and constructs, compares, interprets and evaluates data displays, including tables, picture graphs and column graphs

#### Resources

• At least three balls of approximately equal size made of different substances, eg a squash ball, ping pong ball, golf ball or ball of the same size made of plasticine
• Metre rule or tape measure
• A fairly open area where bouncing balls will do no damage

#### Work, health and safety

Check relevant Work, health and safety guidelines.

#### Evidence of work for assessment purposes

• A description of the method used to test and measure the height of bounce
• Data obtained recorded in a table and displayed in a column graph
• A conclusion relating 'bounciness' to the material used to make the ball

#### STEM teaching and learning activities

• Recall that different substances have different properties and that those different properties determine what the substance might be used for, eg plastic can be used for raincoats because it is waterproof.
• What properties of materials could be useful for making balls?
• Brainstorm the types of different balls used in different games.
• What is it that makes a ball, a ball? That is, what are the essential properties of a ball? For example, do all balls have to be round? Do they all have to be bouncy?
• Examine a selection of balls. Describe the materials they are made from.
• Choose a number of balls, of about the same size, made out of different materials to test how high they bounce.
• Record the height of the bounce in a table. Students should take at least three readings for each ball bounce and calculate the average value. See Constructing and using tables.
• Graph the average height of bounce for each type of ball. See Constructing and using graphs.
• Discuss the information shown in the students’ graphs. Do all graphs show the same information? Do all graphs indicate the same results or results that can be compared? Can this information help students answer their investigative question? This answer will form each student’s conclusion.

#### Vocabulary list

Property – a quality or characteristic of something (not a possession or house). Words used to identify properties: flexible, inflexible, elastic, protective, waterproof, shiny
Material – the matter from which something is made, eg fabric, metal, wood
Elasticity – the ability of a material to go back to its normal shape after having been stretched or squashed (elastic – adjective)
Conclusion – an opinion or judgement based on evidence

#### Key inquiry questions

What material is each ball made from?
Encourage the use of specific words relating to the properties of the material. Encourage the use of senses other than visual and tactile, eg what type of sound does it make when it bounces? How easy is it to squash or stretch?

Why choose balls of a similar size?
Students need to understand the concept of a fair test. It is possible that the size of a ball may affect how high it bounces. As the students are trying to see whether the materials from which the ball is made affects how high the ball bounces, that is the only thing that should be changed in this investigation. Other factors that should be kept the same are the:

• height from which the ball is dropped
• way the ball is dropped
• part of the ball from which the height of the bounce is measured, eg is it measured from the bottom of the ball or the top of the ball?

Is one measurement of the height of bounce enough?
Measuring the height of bounce is the most difficult part of this investigation. One would expect a lot of variation in the measured heights. Because of this, it is good practice to take several readings. This also means that every person in the group gets practice in measuring. The values of the height of bounce are recorded in a table, and then the average of the values is calculated. This calculation, which finds the middle value, reduces the effect of errors.

How can the height of a bounce be measured accurately?
As the height of a bounce is reached very quickly, it is very difficult to take a clear reading against a metre rule or tape measure. When the students are ready to take their values, it is worthwhile for them to bounce the ball a couple of times, before they try to read a value. This will indicate the height to which the ball is likely to bounce and therefore the part of the metre rule to focus on.

If students have the use of a laptop, video camera or iPad, they could video the bounce and slowly replay the recording to read the value on the rule more accurately. Any method the students wish to use is reasonable, so long as they are able to get a value or marking on a sheet of paper, so that they are able to measure the height of the bounce.

What type of graph should be used?
The data shows the height of bounce of different balls. The most appropriate graph for this type of data is a column graph, as each set of data is obtained by using a different ball. The material of each type of ball is the factor that is being changed, therefore, these are the values that will be placed on the X axis. The height that the balls bounce is the factor that is being measured (to see the effect of the different material); therefore these values will be placed on the Y axis. Students need to include a label (with units where appropriate) on each axis, and ensure that the scale of values is even. See Constructing and using graphs.

The following statements outline some common preconceived ideas that many students hold, which are scientifically inaccurate and may impede student understanding.

The word 'material' has a specific meaning in the context of clothing, to mean the fabric (or other substance) used in the clothing. More generally, 'material' means any substance that can be used in a product. For example, the materials used for windows can include glass, wood, aluminium, zinc-coated steel, paint, etc.

The word 'property' is often taken to mean someone’s possession, house or land. In terms of Science, 'property' refers to a characteristic of a substance. For example, glass is hard, transparent and can break easily (brittle).

The smaller/bigger/heavier/lighter the ball, the higher it will bounce.
The 'bounciness' of a ball depends on the elasticity of the material from which it is made. An interesting way to show this is by using an inflatable ball. If the ball is fully inflated, it will bounce because the plastic and the air it encloses has elasticity, ie once squeezed it will re-form its original shape. The transformation of energy (from gravitational potential energy – falling from a height, to the kinetic energy – movement) is almost complete. If the ball is not fully inflated, the energy cannot be fully transformed so the ball does not bounce as high.

#### Support materials

Teacher resources

Student interactive
Plastics: choose the best plastic for different items.

#### Adjustments for the diversity of learners

Students make their own high bounce ball to test against other balls.

Students develop plans for their own type of ball game using their knowledge of other ball games. They include a description of the materials used in the construction of game equipment, eg the ball. They explain why this type of ball was chosen (eg must be able to bounce, must be heavy, and must be able to move by itself). Some of the new games, such as Koolchee: Aboriginal ball game, could be played by the class.

Teacher demonstration

• Make sure you are outside with plenty of room.
• Carefully put the tennis ball on top of a basketball, holding one hand under the basketball and the other on top of the tennis ball.
• Let go of both the balls at exactly the same time and observe what happens.

The tennis ball bounces away at great height. The energy is not only transformed as it would be with one ball being dropped, but it is transferred from the basketball to the tennis ball, giving the tennis ball much more energy.

#### Review

By completing this STEM activity you have provided your students with the opportunity to plan and carry out an investigation, gather data and draw conclusions based on that data. Although much of the investigation was centred on the concept of forces, you have introduced the idea of energy and the concept of the transferal and transformation of energy. This is stated in the First Law of Thermodynamics, which states that energy cannot be created or destroyed, only changed from one form to another. This investigation also focused student experience on the fact that the properties of materials determine the characteristics and uses of the products made with those materials.