1. Friction
When the arrow flies from the bow, it eventually slows down, falls down and stops.
When a ball is thrown into the air, it eventually stops going up and starts coming back down to the ground where although it might bounce a few times, it eventually stops.
When you ride down hill on your bike and you want to stop before you hit the wall, you squeeze the brakes and eventually, good maintenance assumed, you stop.
When the wind blows the sails the boat will move through the water. When the wind stops blowing, the boat will eventually stop
What has surface got to do with friction?
What has shape got to do with friction?
What is friction?
What is actually going on when the arrow stops, the balls drops or you don’t actually hit the wall?

2. Useful Words Friction Air and water resistance Equilibrium Force meter
Vocabulary
Useful Words
Friction
The action of one push or pull acting
against another push or pull where the result is fast transfer of energy spilling into heat and sound
Air and water
resistance
The push back of air or water as an object goes
through. This depends on the shape of the object.
Stillness. All the directions of pushes and pulls on an object are balanced so the object stays still
Equilibrium
Force meter
Used to measure force in Newtons
Newton
A unit of force needed to lift or otherwise move a mass of 100 grams (approximately)
Equilibrium
Stillness: the balance of all forces on an object
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3. Force meters
3 Newtons
7 Newtons
5 Newtons
8.5 Newtons
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4. Forcemeter reading in Newtons
Using Force meters
Try hanging different objects from around the classroom on the force meter Write down the readings you get!
Idea for starting and investigation
Object
Forcemeter reading in Newtons
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5. Force against resistance
A stationary object is at equilibrium. The gravity pull down force is the same as the opposing push up force of the surface.
Equilibrium means balance or equal.
A push force from the side will move the object but the ease of movement depends on the roughness or the smoothness of the surface.
This means the surface causes more or less resistance : greater or less friction or grip.
More force is needed to start the movement on any surface than is need to keep it moving.
The effort depends on the type of sliding surface
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6. Investigation: Which surface do objects slide on most easily?
Which of these surfaces will a weighted box slide across most easily? A) Vinyl B) Wood C) Carpet
When you have chosen, explain why you think this surface will be the easiest to slide across.
Make a careful note of the amount of force being applied just before movement takes place.
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7. Investigation (cont.)
Investigation: Devising a fair test and persevering. Example: Investigate the force needed to move an object over a given distance on a range of surfaces.
The brief says an object over a range of surfaces so we need to list the variables and eliminate those we don’t need.
Variables here are surface, object, weight, distance, slope and force
We keep things simple by:
Making a standard weight e.g. 1kg is approx 10 newtons
Using a flat surface
Using a standard distance e.g. 20cm
The only variable now is the type of surface.
Now we can make a prediction and test the measurable element: the newtons required to start and to continue the movement.
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8. Tyres on a car Playground slide Goalkeeper’s gloves Shoe laces
High and Low Friction
Is it best for each of the following to have a rough or a smooth surface?
Situation
High Friction
Low friction
Tyres on a car
Playground slide
Goalkeeper’s gloves
Shoe laces
A drawer
Ice skates
Climbing rope
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9. Which shape do you think will travel through the water the quickest?
Water Resistance
Which shape do you think will travel through the water the quickest?
Why do you think this one will be the quickest? Test different shapes to see how quickly they move through the liquid.
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10. Water Resistance
movement
water
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11. Friction: the collision of opposing forces
brakes
ice skates
Rough: high friction
Smooth: low friction
tyres
slide
goalkeeper’s
gloves
drawers
Friction:
the collision of opposing forces
Air resistance- the opposing push of air molecules against on an object
moving through air
Water resistance-
the opposing push of water molecules against on an object
moving through air
Big area:
High
resistance
Non streamlined:
High resistance
Streamlined:
Low resistance
Small area:
Low resistance
dart
streamlined car
sail (boat)
parachute
person walking
through water
submarine
fish
boat
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