# Work samples

## Bouncing balls

Students were asked to design an investigation that determines the relationship between the drop height of a ball and its bounce back height. This task was part of a teaching and learning unit on transformation of energy where students explored how energy comes in a variety of forms, including kinetic, gravitational potential and chemical potential energy. During this unit, students also inquired into how transformations between different forms of energy are rarely 100 per cent efficient, as part of the initial energy is often converted into unintended forms of energy, such as heat or sound.

In this investigation, students were asked to determine the percentage of the drop height to which a ball returns on bouncing and whether that percentage varies for large or small drop heights. Students were made aware of the fact that the efficiency of the energy transformation depends on the material the ball is made of and that the bounce percentage is an indicator of this efficiency. They were asked to compare the efficiencies of balls made from a variety of different materials.

Students were asked to submit their results in a report (750 words maximum) in electronic form. They were asked to display the data for each type of ball in graphical form and use the slope of the line of best fit to determine the energy efficiency of each ball. They were further asked to discuss what happens to the energy within the system during a ball’s drop-and-bounce cycle and to calculate the maximum velocity of each ball on impact with the floor when dropped from a height of one metre.

### Achievement standard

By the end of Year 10, students analyse how the periodic table organises elements and use it to make predictions about the properties of elements. They explain how chemical reactions are used to produce particular products and how different factors influence the rate of reactions. They explain the concept of energy conservation and represent energy transfer and transformation within systems. They apply relationships between force, mass and acceleration to predict changes in the motion of objects. Students describe and analyse interactions and cycles within and between Earth’s spheres. They evaluate the evidence for scientific theories that explain the origin of the universe and the diversity of life on Earth. They explain the processes that underpin heredity and evolution. Students analyse how the models and theories they use have developed over time and discuss the factors that prompted their review.

Students develop questions and hypotheses and independently design and improve appropriate methods of investigation, including field work and laboratory experimentation. They explain how they have considered reliability, safety, fairness and ethical actions in their methods and identify where digital technologies can be used to enhance the quality of data. When analysing data, selecting evidence and developing and justifying conclusions, they identify alternative explanations for findings and explain any sources of uncertainty. Students evaluate the validity and reliability of claims made in secondary sources with reference to currently held scientific views, the quality of the methodology and the evidence cited. They construct evidence-based arguments and select appropriate representations and text types to communicate science ideas for specific purposes.