Friction
This Topic is About...
- I will learn where friction happens and what it does.
- I will measure friction on rough and smooth surfaces using a forcemeter.
- I will ask a scientific question and plan a scientific enquiry to find the answer.
- I will choose the best equipment and use it correctly.
- I will link my conclusion to my scientific question.
You’re going to be a science explorer!
Key Words
- friction
- grip
- slippery
- surface
Tap to Learn the Meanings!
- friction: A force that slows things down when two surfaces rub against each other.
- grip: How well something can hold onto or stay on a surface.
- slippery: A surface that has very little grip, making things slide easily.
- surface: The top or outside part of something.
Great job! You’re learning important vocabulary about forces and surfaces.
What is friction?
When one object moves on another object it makes a force called friction.
Friction happens where the outside part of the object, the surface, pushes over the surface of the other object.
The friction pushes against the movement, so it slows down the moving object.
Gravity is pulling this girl down the slide. Friction between the surface of her clothes and the surface of the slide slows her down. The more friction there is the slower she will slide.
Sometimes we use the word grip to describe friction. A surface that has lots of friction has good grip and can be called a grippy surface. A surface that only has a little friction is called a slippery surface.
Rub your hands together. Friction can make your hands warm. Too much friction can burn your skin.
FUN QUESTIONS
1. What does friction do to moving objects?
Show answer
2. Where does the friction happen?
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3. Why do you move so fast on a water slide?
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Let’s Investigate!
Which surface has the least friction?
You will need
- some forcemeters
- an object to pull
- some different surfaces
Method
- Pull your object over a range of different surfaces.
- Use a forcemeter to measure the friction on each surface.
- Try both a very smooth surface and a very rough surface.
- Predict which surface you think will have the least friction.
- Record all your measurements in a results table.
- Use the results to write a clear conclusion.
Think and discuss
- Which surface produced the smallest force reading?
- Did any surfaces behave differently from what you predicted?
- How do your results help you answer the question: Which surface has the least friction?
How am I doing?
Read your conclusion. It should answer the main investigation question: Which surface has the least friction?
Does your conclusion clearly answer this question? If not, rewrite your conclusion to make it clearer.
Show answers
A surface with the least friction will give the smallest reading on the forcemeter because less force is needed to pull the object.
- Smooth surfaces usually have the least friction.
- Rough surfaces usually create more friction and give higher force readings.
- Your conclusion should match the pattern shown by your measurements.
Example conclusion:
“The smooth surface had the least friction because it gave the lowest force reading on the forcemeter.”
Let’s Investigate!
Questions about friction
You will need
- a forcemeter
- some masses
- some water
- some shoes or other objects to pull
Zara and Arun have a new question about friction.
What type of scientific enquiry can they do to find out the answer: research, pattern seeking, observing changes over time, fair testing or identification and classification?
Does a heavier object have more friction?
Zara and Arun can do a fair test to find the answer. They will need to change one thing, measure one thing, and keep everything else the same.
Answer these questions
- What is the thing they will change?
- What is the thing they will measure?
- What things will they need to keep the same to make the test fair?
Now ask your own question about friction that could be investigated using a fair test. You can use the word grid shown in the activity to help.
How am I doing?
Have a look at a friend’s question. Does it make sense?
Have they remembered the question mark?
Can it be investigated using a fair test?
Show answers
Type of scientific enquiry: Fair testing is the correct type because they are changing one variable and measuring its effect.
Fair test questions
- What they will change: the weight (mass) of the object.
- What they will measure: the amount of friction, shown by the forcemeter reading.
- What they will keep the same: the surface, the type of object, how far it is pulled, the speed of pulling, the forcemeter used.
Example “own question” a student might ask:
“Does adding water to the surface increase the friction?”
General rule: A heavier object usually produces more friction because it presses down harder on the surface.
Investigation Steps
Investigate one of the questions.
Plan the fair test by drawing a diagram to show what you will do.
Write a conclusion to show what you find out.
Make sure your conclusion gives the answer to the question.