Teaching activity - Exploring elasticity

Level 3 and 4
Nature of science: Investigating in science
Students will:

• build on prior experiences, working together to share and examine their own and others’ knowledge 
• ask questions, find evidence, explore simple models, and carry out appropriate investigations to develop simple explanations. 

Level 3 and 4
Physical world: Physical enquiry and physics concepts
Students will:

• explore, describe, and represent patterns and trends for everyday examples of physical phenomena, such as movement, forces, electricity, magnetism, light, sound, waves, and heat. For example, identify and describe the effect of forces – contact and non-contact – on the motion of objects, and identify and describe everyday examples of sources of energy, forms of energy, and energy transformations. 

Level 5
Nature of science: Investigating in science
Students will:

• develop and carry out more complex investigations, including using models 
• show an increasing awareness of the complexity of working scientifically, including the recognition of multiple variables 
• begin to evaluate the suitability of the investigative methods chosen. 

Level 5 
Physical world: Physical enquiry and physics concepts
Students will:

• identify and describe the patterns associated with physical phenomena found in simple everyday situations involving movement, forces, electricity, magnetism, light, sound, waves, and heat. For example, identify and describe energy changes and conservation of energy, simple electrical circuits, and the effect of contact and non-contact on the motion of objects. 

Being able to measure is an important skill within all cultures. Early Māori had a comprehensive set of units that were used in measurement.  

To learn more, see Early Maori measurement on the Science Learning Hub - Pokapū Akoranga Pūtaiao and MOTAT’s Inenga: Early Māori measurements. 

In this activity, students explore forces in action. Specifically, they will see that the amount of distortion of a material increases in proportion to the force applied – within limits.  

By conducting experiments to gather data about the stretch in a rubber band, students are modelling scientific investigations and beginning to explore relationships between force and energy. 

• Energy cannot be created or destroyed. It changes from one store of energy to another (see the BBC’s Energy stores article). 
• A stretched or squashed object has more energy in its elastic potential energy store. 
• Gravitational potential energy is stored in an object because of its distance above ground and its mass. 
• The amount of energy in the kinetic energy store depends on the speed of the object. 

• Students will:

  • Make predictions as to how much weight a rubber band can hold
  • gather and interpret data as bands are loaded (Five science capabilities)
  • record data
  • identify patterns in data (Five science capabilities)
  • use evidence to develop a "rule of stretching" that connects the amount of stretch and the amount of weight. For example, does doubling the weight double the amount of stretch? (Five science capabilities)

What you need: 

• a range of different sized rubber bands 
• sets of hanging weights, about 250 g each, totalling about 3 kg per set – or 25 N force metres 
• two small double-ended hooks per group 
• one 30 cm ruler per group 
• a selection of springs and appropriate weights – see other ideas to use this resource.        

For teachers: Guiding student exploration 

1. Explain to students that they will be designing an investigation and predicting patterns between stretch and load in rubber bands and springs. 
2. Provide a variety of different rubber bands for students to explore and compare their stretchiness – thickness, size of band. 
3. Ask students to pair share, record, and feed back what patterns they predict load has on how much the bands will stretch.   
4. Show them the rest of the equipment available, then ask them to discuss in groups how they could set up an experiment to test their predictions. 
5. Ask students:  

• What evidence will you need to support these predictions? (Measure relationship with different variables) 
• What variables could you measure, and how could you record your data systematically? (Measure the length of one type of rubber band with different weights to determine stretch, measure the length of different rubber bands using one weight.)

Example of recording in a table: 

6. Invite each group to set up their equipment and record their measurements. Ask them to make a note of any problems they have noticed with their method. 

7. Have each group compare their data with the other groups and discuss as a class any patterns in the relationship between stretch and load. 

Reflection questions for discussion:  

• Did you obtain any data that supported your predictions? Why / why not? 
• Did you find any limits to your predictions? If you did, what do you think the reason was? 
• Why might you find it difficult to test the stretching of springs? 
• What new evidence would you need to gather to formulate a law about all elastic materials?   

• What happens when a rubber band under tension is heated? See Rubber Band Thermodynamics by Chris Cramer on Youtube 
• Science Learning Hub - Pokapū Akoranga Pūtaiao: 
  • Alternative conceptions of energy 
  • Calculating potential and kinetic energy 
• Upstart magazine’s How to Make Your Own Bow and Arrow  
• Slingshots: Slingshot Science: The Physics in Angry Birds