Why do balls roll? Why do apples fall from the trees? Why do some things slide across ice but not on carpet? What makes our bikes stop when we brake? We use all types of forces including friction, gravity and pushes and pulls when we exercise, ride bikes and drive cars. Engineers and Scientists use their knowledge of forces and motion to design things for our homes, work and school.
Last week we looked at friction by:
- Observing how friction is different with different surfaces
- Exploring what more or less friction feels like
- Using arrows to represent frictional forces
Friction is what happens when any two things rub against each other causing grip.
Our first experiment involved everyone wearing rubber gloves. We then had to rub our hands together and describe what it felt like. Some of our answers included
- hands becoming hot
Then everyone was given a small sample of detergent in their hands and we had to rub our hands again with the detergent and describe what it felt like. Some of our answers included:
- easy to move your hands
We discussed how the material that the glove is made of enables us to feel more grip when we rub our hands together. We also talked about how there was more friction when rubbing our hands together without the detergent than with the detergent because there was more grip. The more grip we have, the more friction there is between two objects.
We then worked in small teams to investigate the friction force between different surfaces. The surfaces included:
We had to predict which surface would cause the most friction before testing each one. We used our trays as a heavy item that we had to push across each surface.
Most teams found that the grass surface caused the most friction when pushing the tray and the table top having the least amount of friction occurring.
To make something move, we need to apply enough force (transfer enough energy to the object) to overcome the force of friction trying to stop that movement. This can be more difficult at times depending on the surface and object.
What did you learn about friction?
Which surface did you find caused the most friction and why?
Can you give an example from everyday life where friction plays a role?