1. 21/04/ Friction
Watch as your teacher demonstrates ways to reduce friction. You may have seen these before, in 2nd year. Take notes if you wish.

2. Work in pairs - Attempt to fill in the 7 blank spaces in note 18.
Open up your notes at page 13, note 18, Friction, and collect a highlighter or coloured pen.
Work in pairs - Attempt to fill in the 7 blank spaces in note 18.
two moving
moving
against
moothing
eparating
streamlined
smoother

3. Work in pairs - Attempt to fill in the 4 blank spaces in notes 19, Tension and 20, Reaction Force.
ope
tension
weight
reaction

4. Problems on page 30 and 31, Q. 11 & 12 to be done first!
Friction (National 4)
1. What do two surfaces have to do to create the force called friction?
2. Does friction try to stop surfaces moving, or make the surfaces move faster?
3. Here are 3 pictures of touching surfaces:
Touch and move in opposite directions.
Frictions tries to stop surfaces moving.
Picture Picture Picture 3.
(a) Which picture shows the surfaces that would have most friction if you
tried to move them over each other.
(b) Explain your answer.
Picture 2
Picture 2 has the roughest edges.

5. (a) Friction between car tyres and the road.
4.In these pictures, write down the surfaces which are rubbing together to create friction.
Sole of boot and road,
boot and air
Tyres and road,
air and car, air and person
Boat and water,
boat and air.
5. Friction is sometimes very useful (good) and sometimes a pain (bad). For each of the following examples, state whether friction is good or bad.
(a) Friction between car tyres and the road.
(b) Friction between your shoes and the ground.
(c) Friction between skis and snow.
(d) Friction between a climber’s rope and hands.
(e) Friction between a speed boat and the surface of the water.
Good
Good
Good to get going, bad when wanting to go faster
Good
Good to get started, then bad when wanting to go faster!

6. 6. Friction can be reduced on rough surfaces by smoothing or separating the
For each diagram below, state how friction between the surfaces is being
reduced.
oil
Diagram A Diagram B
Surfaces have been smoothed
Lubrication has been put between
surfaces.

7. 7. A foot in contact with the ground produces a lot of friction
7. A foot in contact with the ground produces a lot of friction. How is an ice skater’s boot designed to reduce friction.
Surfaces of the blade is smooth and surface area, in contact, is reduced.
8. For each of the following, suggest how friction can be reduced.
(a) A stiff door hinge.
(b) The design of a fast car.
(c) Snow boards on snow.
(d) An air hockey puck on its table.
Oil hinge.
Streamline the shape.
Streamline the shape and wax.
Add air to separate surfaces.
9. For the following situations where friction is useful, suggest how friction can be increased.
(a) Cars sliding on icy roads.
(b) Vehicles having to stop at dangerous junctions.
(c) Farm vehicle tyres sliding in the mud.
(d) A gymnast’s hands sliding on the bars.
Grit roads or snow tyres.
Change road surface
to increase friction.
Put rubber mats under tyres.
Chalk hands.
10. Objects can be “streamlined” in order to reduce friction.
(a) State 3 ways that a vehicle can be streamlined.
(b) Describe how a cyclist can make himself streamlined.
Rounded shape, reduce height and width.
Wear a “tear drop” shape helmet and wear tight fitting clothes.

8. Tension and Reaction Forces (National 5)
11. For each of the following situations, state whether the force, F, is a Tension
force or a Reaction force. F
weight
2kg F F
(a) (b) (c)
Tension
Reaction
Tension
(d) (e) (f) F
weight
push F F
Tension
Reaction
Reaction
12. Copy and complete this sentence
Every force has a _______________ force that is equal and opposite to it.
A _______________ force is a “pulling force” through a connecting wire or
rope or bar.
reaction
tension