Subject focus: KS2 Science
Pupils should be taught to...
recognise that some mechanisms, including levers, pulleys and gears, allow a smaller force to have a
(National Curriculum 2014, Science, Year 5, Forces.
Subject focus: KS2 Design andTechnology
Pupils should be taught to...
Understand and use mechanical systems in their products [for example, gears, levers, cams, pulleys
(National Curriculum 2014, Design and Technology, KS2, Technical Knowledge.
Suggested Classroom Activity
Explain to the children that today they will be performing a virtual autopsy on a mechanical horse. (Ignore the cries of 'Not Again!') Show them video 1. Ask children to draw what they think the inside of the toy horse would look like, then share the results in small groups and report back to the class with their favourite ideas.
Show video 2 of the inside of the toy, and ask them to describe what they think is happening and discuss what aspects of the children's own ideas seem to have been accurate.
Organise them into small groups around computers pre-loaded with video 3 of three different pairs of cog wheels rotating. This is the crux of the lesson. Their task is to carefully observe the film and accurately describe what they see, and what mathematical pattern they observe between the wheels and their speeds of rotation. They will need to pause the video in order to be able to count the cogs, and play it to count the rotations of the wheel. In the first pair, the red wheel has 12 cogs and the grey wheel, 6. The grey wheel rotates twice per each rotation of the red. The second pair of wheels are both 12 cogs. They rotate at the same speed. The third pair, the red wheel has 18 cogs and the grey wheel, 12.
How many times does the horses tail turn during a single revolution of the blue spring wheel?
The desired result is for the pupils to express the theory that the relative speed of the wheels is governed by the number of cogs. A formal description would be; Applied to the last pair of wheel on the film clip, that would read. Rotation speed of wheel B = cogs wheel A over cogs wheel B. Applied to the last pair of wheels in the film that would read, Rotation speed of grey wheel= cogs red wheel=18 over cogs grey wheel= 12 so 1.5 times faster.
Play video 4 and ask the class to count along with the rotations. (It spins 5x4x4 = 80 times)
Discovering and applying the formula behind gear ratios.
The core task involves pattern seeking, one of the main types of scientific inquiry required by the National Curriculum.
The whole lesson also provides ample opportunity for pupils to develop their use of scientific spoken language.
"The national curriculum for science reflects the importance of spoken language in pupils" development across the whole curriculum, cognitively, socially and linguistically. The quality and variety of language that pupils hear and speak are key factors in developing their scientific vocabulary and articulating scientific concepts clearly and precisely.
They must be assisted in making their thinking clear, both to themselves and others, and teachers should ensure that pupils secure foundations by using discussion to probe and remedy their misconceptions."