Lesson 6 Decontamination

# Episode 3

Reasoning Resources: Worksheet 2, angle measurer (optional), scrap paper. Worksheet 3 on board or OHT
Shifting attention from discrete quarter turns to continuous smooth turn, through intermediate turns. Whole class preparation: introducing smooth-turns in the LOGO and bearings conventions
All estimations are linked to some clear reference values. For angles, they are related to the intuitively assimilated right angle (90°).

Preference for simple tools for approximate measurements.
There are other types of robot that don’t need to go directly south, or turn left, etc. but can go directly from the landing point to the toxic waste. What will we need to use to make that happen? Pupils may have already recognised the possibility of intermediate compass moves, e.g. NW and SE. Possible answers include: ‘Go diagonally’; ‘Use north-west’; ‘Go straight there’; ‘Use angles’. Ask pupils to estimate the angle you are turning with an extended arm forward from the board to the corner, from the corner to the door etc. Get the class to explain their estimates in terms of half or quarter of a right angle. Extend to degrees. Indicate that for the purpose of this activity angles correct to 5 or 10 degrees are acceptable, to avoid the need for protractors. As a rough tool, they can use a corner of a sheet of paper folded in half to make 45° and in half again to make 22.5 degrees, or folded three ways to make 30 and 15 degrees,

Explain to the pupils the main two different ways of measuring angles of turns. In one the measurement is left or right from the way one is facing, which can be called LOGO convention after the turtle and ‘big-truck’ games they may be familiar with. Explain how for the LOGO robot the angle to turn through is measured from the way the robot is facing. This turn can be a rotation to the left or to the right. The other is the bearings convention where the angle is measured starting from north and turning clockwise.
Pair/small group work
LOGO is a software package in which a turtle turns through an angle relative to the direction in which the turtle is facing.

Clockwise is a useful convention. Left/right is not sufficient without knowing
the way the turning object
is facing.

It is not necessary to give a direction to the Bearings robot because they are always measured ina
clockwise direction from north.
Groups or pairs could choose to use either convention and program the robot from one landing place to visit both sites and return to the landing point. Each pair needs a new copy of Worksheet 2 and an angle measurer or paper folded into different angles, as described above.
Pupils should work out instructions for their new robot and then share their work with a pair who have worked with the other convention.

The key questions here are: What do you do to work out the homeward journey for your robot? What are the links between the Bearings robot and the LOGO robot? Can you turn instructions for a Bearings robot into instructions for a LOGO robot and vice versa? Which method of giving directions is easier? Why?
Whole class sharing/discussion
Return journey which retraces the same steps by each robot can be linked step by step to the onward journey. But the comparison between the two conventions is elusive. It would be rewarding only for some pupils to explore this in numbers. Discuss the links between the two different robots, including the similarities and the differences. Discuss how to ‘undo’ the instructions given to each robot. Which robot is easier to use?
End of Lesson Reflection
The triathlon map is intended to be projected and discussed. It is important that pupils appreciate which method to use, rather than actually needing to do it.
• What have you realised now that you weren't aware of at the start of the lesson?

Expect responses of the type: ‘How important the grid is and knowing which way round the map is.’ ‘There are loads of ways of giving directions, I hadn’t really thought about that before.’ ‘There are all these ways but I just use left and right'.

• In what situations would you use each of the four methods?
• The questions and the map showing a triathlon race, on Worksheet 3, could act as prompts for this discussion.