3Turn-7

Outcomes

• Pupils can sketch the shape of Force verses Extension graphs for helical springs

Specification References

1.27 describe how extension varies with applied force for helical springs, metal wires and rubber bands 1.28 recall that the initial linear region of a force-extension graph is associated with Hooke's law 1.29 associate elastic behaviour with the ability of a material to recover its original shape after the forces causing deformation have been removed.

Starter

AFL Talk partners Why might it be useful to know how stretchy things are? • Give each pupil spring to promote ideas – CARE NOT TO BREAK! • Discuss ideas as a class – feedback from one person in pair

Main Body of Lesson

1. Investigate springiness! Demo experimental set up Highlight safety points - safety glasses and the top loop of spring should be wound with string to stop it from unwinding

2. The students will carry out a force extension graph for a spring. Discuss variables From changing the mass and measuring length – how can we calculate force and extension?

3. Students get on with collecting data GOGGLES NEEDED! Take spring beyond elastic limit – approx. 1.1kg

4. Plot graph of force against extension Display example axis Make a conclusion. What do you notice? Was this what you expected?

5. Pack all equipment away

Plenary

Condensing - What is the most important thing you have learnt today?

Homework

Read P 60-61 and answer questions

Additional Information

Resources Required

Class set - experiment on force vs. extension of spring. Students will need to support a ruler vertically and will need some sort of pointer Springs, rulers, clamp stands, masses

Safety/Hazards

Goggles to be worn during all stretching activities due to the chance of something pinging off 
Ensure pupils do not flick elastic bands at one another or across the room! 
Mass may fall off and fall on feet - ensure pupils stand during practical 
Weigh down the clamp stand to prevent any tipping 

Notes

The wikipedia page on mental chronometry is very good, especially the types of tests available. Average response time for simple visual stimuli is 190ms