A brick and samples of the following surfaces: carpet, wood, vinyl, ice
Friktion - interaktivt
Demonstrate trying to pull a brick with a Newton meter on the carpet and the vinyl samples. Which surface is it more difficult to get an object to start moving on – a smooth or a rough surface? Why? Encourage the children to explain their ideas using words such as roughness, smoothness, grip and slide or slip. Explain that where there is greater grip, there is a greater force of something called friction.
Show the children the four different surface samples. Explain that they are going to carry out a virtual experiment to find out on which surface a sleigh will travel furthest. They are going to start the sleigh moving with a push. Discuss what will need to happen to make sure this is a fair test (same size push, same sleigh). Open the online activity on an interactive whiteboard and demonstrate how to select a different track surface, and how to start the sleigh moving. On which surface do you think the sleigh will move the furthest? On which surface do you think the sleigh will move the shortest distance?
Arrange the children in pairs or groups, with a computer for each group. Ask children to work through the activity, following the tasks written (and spoken) at the top of the screen. Ask them to record distances travelled (or flags reached) on paper.
Were their predictions right? Discuss why the sleigh does not travel as far on the carpet, even though it received the same size push as on the other surfaces. Again, encourage the children to explain their ideas using words such as roughness, smoothness, grip, slide and slip. Is there more friction between the sleigh and the carpet, or between the sleigh and the ice? Develop the link between grip and the force of friction. What does this indicate about road surfaces? How do we make sure cars and bicycles are going to be safe? What will happen in the winter when the roads are icy?
Ask children to complete the online quiz on Friction.
Draw and describe the soles of different pairs of shoes in their house. Which have more grip and which will they be likely to slip in?