PHYSICS FOR THE IB DIPLOMA: TEACHER’S RESOURCE

1 How far have you gone? (2 minutes)

Resources: n/a

Description and purpose: Ask students to sit in the same positions as they did in the previous lesson that was held in the same room. Now ask them to discuss with a learning partner how far they have travelled since the previous lesson. The answer could be several kilometres, for example, around the school, to home and back, and so on. Alternatively, the answer could be no distance, because they have ended up in the same place as last time. Use the idea to introduce the difference between distance and displacement.

2 How fast? (10 minutes)

Resources: A number of photographs, pictures or videos from the internet of animals, runners, cars, aeroplanes, the Earth moving round the sun and so on.

Description and purpose: Ask students to place the objects in the pictures in order from slowest to fastest. In groups, students can suggest values for the top speed of each object. Groups can then compare their results. As students discuss results, it should become clear that speeds can be measured in different units. Write some typical results on the board so that students can self-assess their estimates. Ask: Do you understand the different units that you use?

Challenge students to come up with as many different units for speed as they can. Ask: What units might an astronomer use to measure the speed of a galaxy moving away from us?

1 Using the equation for average speed (20 minutes)

Resources: Calculators, Coursebook Test Your Understanding questions

Description and purpose: Briefly explain the equation for speed. Point out that average speed is calculated from total distance total time

Introduce the SI system of units. Explain the need for an international system. Ensure that all students can rearrange this equation successfully. Do they understand how to convert between different units of distance, such as millimetres, centimetres and kilometres? Do they understand how to convert between seconds, minutes and hours?

Teach students how to set out their answers clearly, with the formula, substitutions, calculations and units all being shown. For example: distance = speed × time = 3.6 × 5.2 = 18.72 = 19 m (to two significant figures)

You should make this an essential requirement when setting out answers: ask students to add the necessary detail if they do not show their working in homework or class exercises. The aim is for students to give this detail automatically. Note: using the same number of significant figures for the answer as in the data is not always necessary at this stage. But you might like to introduce it so that students get into a good habit.

Students can use Test Your Understanding question 1 from the Coursebook to practise the calculation.

Assessment ideas: Give students questions and ask them to mark each other’s work. They can explain in their own words to each other why an answer is incorrect.

Differentiation: Some students prefer to use a formula triangle to display the relationship between speed, distance and time. This may be helpful at the start, but they will eventually need to be able to rearrange simple formulae without aids. Encourage students to stop using aids as soon as they are confident.

Reflection: If students have made mistakes in calculations, ask them to consider how they might avoid this in the future.

Language focus: The word ‘per’ in units, such as metres ‘per’ second, means ‘in each’. So, 5 m s−1 means 5 metres in each second.