GEARS Explore Cambridge related themes gears CYCLING FORCE
Key Stage 2 Lesson: How Do Gears Work? National Curriculum Science Objectives: Upper Key Stage 2: Recognise that some mechanisms including gears allow a smaller force to have a greater effect. Cross- Curricular Link: Literacy Retrieve, record and present information from non-fiction. Preparation Prior to this session, set children homework to ride their bikes uphill, downhill and on the level, choosing the most appropriate gear selection for each gradient. Ask those who do not have bikes (or don t have bikes with gears) to watch the video clip: How Do Bike Gears Work? As children watch the video ask them whether the woman is pedaling more or less when she travels uphill compared to on the level. Resources: Video clip: How Do Bike Gears Work? https://www.youtube.com/watch?v=oaudyiu_swm Resource 1: Gears Diagram (separate PDF provided) Resource 2: Gears! Gears! Gears! Wacky Factory s Building Set or similar Resource 3: Small sticky spots (2 per child) Resource 4: Cogs cut-out templates (in this document). More sticky spots, thick cardboard, paper fasteners, blu-tack, scissors
Starter Activity: Read the section of Exploring Cambridge in which Dad decides to travel by bike. Ask children: How does Dad want to travel? Where do they visit by bike? Do they cycle quickly or slowly? How do you know? Elicit that they cycle quickly. Explain that today children are going to be learning about bicycle gears. Ask children if their own bikes have any gears, and if so how many. What gear do children think Dad would use to cycle quickly on the flat? Do they know why that particular gear is a good choice for cycling quickly on level ground? Don t tell them whether their responses are correct, but say that today they are going to experiment to find out which is the best gear for cycling quickly and why. Main Activity 1: Watch the Youtube clip: How Do Bike Gears Work? Ask children who found it easier to cycle uphill, the man or the woman. Can children explain why the woman found it easier to cycle uphill than the man and which gear she chose? Elicit that she chose a low gear which made cycling uphill easier because the pedals are less stiff, but that she had to pedal more quickly that s the tradeoff! The low gear allowed the woman to apply less force to the pedals (torque) than she would have had to without the gear in order to get up the hill. Now that children know a low gear is best for cycling uphill, can they deduce what gear would be best for cycling quickly on the flat? On the IWB, show children the diagram of bicycle gears Resource 1_Gears Diagram (separate PDF).
Ask them what the visual difference is between the high gear and the low gear chain by comparing gear sizes and the number of teeth. Help them to identify that each circle is called a gear, that gears linking together make a gear chain and the prongs are called teeth. Say that you want children to build a high gear and a low gear chain using a construction kit like The Wacky Factory s Gears! Gears! Gears! (resource 2). Say that the children s model gears will interlock and not be linked by a metal chain like bike gears but that they will still work in the same way. Plenary: Now that children have built a high gear and a low gear chain ask them to tell you again what the difference is visually. Explain that a low gear chain is called low because the ratio between the gear circles is low, and the opposite is true for a high gear chain. Which gear did the woman use to cycle uphill? Which of their model gears do they think Dad would have chosen to cycle very fast around Cambridge?
Main Activity 2: In this activity children are going to work out why Dad would have chosen a high gear to cycle quickly around Cambridge. Give each child two sticky spots (resource 3). Ask them to put a sticky spot on one tooth of each gear circle in the high gear chain they made in Activity 1. Children use the sticky spots as a marker to help them compare the number of rotations of each gear. For instance if they turn one of the gears twice, will the second gear also turn twice or is it more/less than that? Repeat the experiment with the low gear chain they built in Activity 1 to help them to decide why Dad would have chosen a high gear to go fast on the flat. Main Activity 3: Children use Resource 4 (cogs cut-out templates) to build their own gear chains. They use sticky spots to compare gear turns as they did in Activity 2. Plenary: Using the results of their Activity 3 experiment, can children suggest which gear combination would be best for travelling downhill? Why do they think that?
Extension Activities Elicit that gears allow a smaller force to have a greater effect (in other words you travel further for less physical effort). Challenge children to carry out research on the Internet to find all the different uses for gears in everyday life they will make some surprising discoveries. Hand whisks, toys, clocks and even vacuum cleaners all use gears. Children make presentations of their findings to share with their peers.
Resource 4 (cogs cut-out templates) for making your own gear chains. Spray mount the cog shapes on the next page onto some thick card. The card needs to have some thickness but still be thin enough to cut with scissors. Cut out the cardboard cog shapes (using different sized cogs to make different sized gears) and use paper fasteners to fix the cogs to a second piece of card to make a gear chain. Use sticky spots to compare gear turns as you did in Activity 2.