Land Yacht

• Review the online pupil material. Use a projector to share this material with your pupils during the lesson.
• Make sure that you have covered Newton’s three laws of motion in an earlier lesson.
• Consider the abilities and backgrounds of all your pupils. Differentiate the lesson to make it accessible to everyone. See the Differentiation section below for suggestions.
• Set up the fans on the floor, allowing at least 3 metres in front of each, so that the land yachts have room to move. Use a strip of tape to mark a start position in front of each fan (perpendicular to the fan).

• Watch the pupil video here or access it via the online pupil material.

• Facilitate a quick discussion about which force makes a land yacht move.
• Ask questions like these:
  • Which forces did you see in action when you were watching the sailboat and kite in the video? (pull/push)
  • Which force made the sailboat move? (It was the push force of the wind.)
• In what situations does a sailboat not work? (If the wind is blowing straight towards the sailboat, the boat cannot sail directly forwards into the wind.)
• Tell the pupils that they are going to build a land yacht and investigate how wind force can change its motion.

• Ask the pupils to work in pairs to build the Land Yacht model. Tell them to take turns, one partner searching for the bricks while the other builds, switching roles after each step has been done.
• You can find building help in the Tips section below.
• Direct the pupils to the three experiments that are found in the pupil material for this lesson. Distribute the Student Worksheets (Teacher Support – Additional Resources).

Experiment 1: Downwind

• Ask the pupils to set their land yachts on the start line, facing away from the fans.
• Tell them to switch the fans on and to let their land yachts blow downwind (straight away from the fans) and to observe their movement. The sail angle can be adjusted by turning the small gear to optimise the land yacht's movement. The red bushings can also be moved to change the shape of the sail.
• Challenge your pupils to find the best sail angle and shape for making the land yacht travel the farthest distance.
• Have them record the best angle and shape on their Student Worksheets.

Experiment 2: Crosswind

• Ask the pupils to set their land yachts on the start line at a right angle, 90 degrees perpendicular to the fan.
• Have them switch the fans on to see if their land yachts move to the side of the fan. (They will have to adjust the angle of the sail again to optimise the land yacht's movement.)
• Challenge your pupils to find the best sail angle, and then record it on their worksheets.

Experiment 3: Into the Wind

• Have the pupils turn their land yachts slightly off the start line and towards the fan to see which sail angle can make the land yacht drive ‘upwind’ towards the direction the wind is coming from. They can use the angle measurement tool from their sets to measure the upwind angle of the land yacht from the line. With the right adjustments, the pupils will be able to make their land yachts move upwind but not directly into the wind.

• Gather your pupils together to review and discuss their experiments.
• Ask questions like these:
  • Which angle was best for each experiment?
  • What were the limits? (Too much wind at the wrong angle can make the land yacht tip over. That is why sailboats ‘reef’ their sails to reduce the surface area of the sail, so that the boat does not blow over and capsize).
  • Why can’t the land yacht go more than 45 degrees upwind (towards the fan)? (The sum of the force vectors acting on the vehicle pushes it downwind.)

• If time permits, explain the forces that are at work (force vectors) in detail.
• Allow time for the pupils to disassemble their models, sort the bricks back into the trays and tidy up their workstations.

• Give feedback on each pupil's performance.
• Facilitate self-assessment.
• To simplify the process, you can use the assessment rubrics that have been provided.

Observation Checklist

• Measure your pupils’ proficiency in describing how different forces can change an object's motion.
• Establish a scale that suits your needs. For example:
  1. Requires additional support
  2. Can work independently
  3. Can teach others

Self-Assessment

• Have each pupil choose the brick that they feel best represents their performance.
  • Green: With some help, I can describe how an invisible force can change an object's motion.
  • Blue: I know I can describe how an invisible force can change an object's motion.
  • Purple: I can describe and explain how an invisible force can change an object's motion.

Peer Feedback

• Encourage your pupils to assess their peers by:
  • Using the brick scale above to score each other's performance
  • Presenting their ideas and giving constructive feedback

Model Tips

• Have the groups start testing as soon as they have finished building. They should take turns as they adjust the sails to ensure that everyone has a chance to try out their models.
• Choose ONE fan speed setting for all the tests. Any speed will do.
• If your fan is too big or too powerful, try moving it farther back from the start line. You could also use a piece of furniture to block some of the fan's airflow.
• If your fan is too small, move it closer to the models or try moving the fan by hand, following the models.

Simplify this lesson by:

• Having your pupils set the sail at 90 degrees for each of the tests

Increase the difficulty by:

• Encouraging the pupils to adjust the shape of the triangular sail
• Challenging your pupils to figure out how to make the land yacht move upwind

(Note: This will require additional time.)
To incorporate the development of maths skills, have the pupils let their land yachts go at a 60-degree angle from the start line and measure how far they travel by counting how many revolutions the rear wheels made before stopping. They can use the angle and distance travelled to calculate the area of the triangle that was created.

Rear wheel diameter = 43.2 mm

• Circumference of the wheel = (π x D = C)

ACMMG197
Investigate the relationship between features of circles such as circumference, area, radius and diameter. Use formulas to solve problems involving circumference and area