Lesson Plan

2. Investigate Hooke's law

KS3-12-02

Intent

Learning Intention

  • Describe Hooke's law
  • Explain what a spring constant is
  • Safely carry out a practical
  • Accurately record results on a graph

Lesson Outcomes

  • State Hooke's law
  • Investigate Hooke's law safely
  • Measure length, calculate extension and plot a graph with a line of best fit

National Curriculum

  • Know about force-extension linear relation: Hooke’s law as a special case
  • Forces measured in Newtons, measurements of stretch or compression as force is changed
  • Forces: associated with deforming objects; stretching and squashing

Working Scientifically

  • Select, plan and carry out the most appropriate types of scientific enquiries to test predictions, including identifying independent, dependent and control variables, where appropriate
  • Use appropriate techniques, apparatus, and materials during fieldwork and laboratory work, paying attention to health and safety
  • Make and record observations and measurements using a range of methods for different investigations; and evaluate the reliability of methods and suggest possible improvements

Resources

Resources: A spring or rubber band, slotted masses, a ruler, a clamp, a boss and stand, a G-clamp and the handout. 

Handout: An investigation sheet for the students to complete on Hooke's law, followed by several activities on springs. 

Rocket words

  • elastic limit
  • Robert Hooke
  • extension
  • spring constant
  • directly proportional

Implementation

Prior Learning: 

Review the keywords ‘compression’ and ‘deformation’ from lesson 1.

Starter

Ask the students why they think springs are important and where they can be used. Ask them to sort their ideas into a mind-map. 

Main Teaching

Use the presentation to discuss how we use springs in everyday life. Link to forces being applied and elastic deformation. Introduce Hooke’s law and the calculation as a way of measuring elastic deformation; then, complete the practical. The students can also discuss how spring constant varies between springs.

Career Film: This is Myles Carey. Myles works as a Mechanical Engineer for Orano. Click on the tour to learn about Myles' job.

Expert Film: Myles Carey works as a Mechanical Engineer for Orano. Myles explains Hooke's law.

Mission Assignment

The students will investigate the relationship between force and spring extension.

  1. Set up a clamp, boss and stand so that the clamp hangs over the edge of the desk. Clamp the stand to the desk.
  2. Hang a spring or rubber band from the clamp and measure its length unstretched. Record this in the box below. NB: the rubber band may need to be flattened to gauge its length.
  3. Hang a slotted mass from the spring/band and measure its length. Then, subtract the original length from its current length to find the extension.
  4. Record this information in the table below.
  5. Repeat steps 3-4, adding an additional mass each time.

Differentiated tasks

Support: A simplified version of the core handout.

Challenge: A space for the students to list as many examples as they can of uses for springs. 

To take it further, ask the students to write a paragraph about Hooke’s law to explain how it works. Ask them to write the paragraph in simple language so a year 6 student could understand. Use the keywords spring, stretch, longer, shorter, weights and measure.

Impact & Assessment Opportunities

Plenary

Students reflect on their ability to complete the practical safely and the use of their communication skills. They can also justify if their results are valid or not after taking the interactive assessment quiz.

Teacher Mastery

Hooke's law is a principle in physics that describes the relationship between the force applied to a spring and the resulting deformation of the spring. It states that the force required to deform a spring is directly proportional to the amount of deformation produced, as long as the deformation does not exceed the elastic limit of the material.

In mathematical terms, Hooke's law can be expressed as:

F = -kx

where F is the force applied to the spring, x is the displacement of the spring from its equilibrium position, and k is the spring constant, which is a measure of the stiffness of the spring. The negative sign indicates that the force is opposite in direction to the displacement.

Hooke's law applies to any elastic material, not just springs. The law can be used to calculate the amount of deformation produced by a given force, or the amount of force required to produce a given amount of deformation. It is widely used in engineering and science to design and analyse structures and materials that involve elastic deformation.

One limitation of Hooke's law is that it only applies to small deformations, where the material behaves elastically. When the deformation exceeds the elastic limit, the material undergoes plastic deformation, and the relationship between force and deformation becomes more complex. Additionally, the law assumes that the material is homogeneous and isotropic, meaning that it has the same properties in all directions. In reality, many materials have complex properties that vary depending on the direction of deformation.