# Friction 2

In this worksheet, students will answer questions about the forces of friction which are created by pushes and pulls.

Key stage:  KS 2

Curriculum topic:   Forces

Curriculum subtopic:   Resistance and Friction

Difficulty level:

### QUESTION 1 of 10

Friction is the name of force which is created when two surfaces rub together.

Here is a boy riding his bicycle.

• The friction between the tyres and the road prevent the rider slipping and skidding.
• The friction between the brake blocks and the wheel slows the bicycle when he applies the brakes.
• The friction between his hands and the handlebar grips prevents his hands slipping.

Friction SLOWS MOVING OBJECTS and prevents objects STARTING TO MOVE. Friction is measured in Newtons, just like pushes and pulls, using a forcemeter.

OK, let's have a look at what's going on with friction.

Choose the best word to complete this sentence:

Friction occurs between...

surfaces

forces

Now think about moving objects and what's going on with friction.

Choose the best phrase to complete this sentence: "When an object is moving, friction... "

slows it down

speeds it up

has no effect

When friction occurs,  which form of energy do you think is produced?

light

heat

electrical

Which THREE of these activities produce heat due to friction?

rubbing hands together

the sun rising

applying the brakes

a gas oven turning on

rubbing two sticks together

When ROUGH surfaces rub together, the amount of friction created is...

large

small

not measurable

Below are five objects which will move over another surface (like the ground).

Which THREE of these examples produces a large amount of friction?

ice skates

knobbly tyres

walking boots

skis

sand paper

Pete has a new skateboard.  He notices that the grip-tape on top of the deck is rough.

This is to create...

high friction

low friction

no friction

Pete applies a force to the wheels of his skateboard. He notices that they spin for a long time.

This is due to...

heat

low friction

high friction

Which TWO reasons explain the need for low friction on this part of the skateboard?

to make it easy to start moving

to make heat

to keep it moving

to stop it moving

At the skate park, Pete skates on the half-pipe.

Why do you think the surface of the half-pipe is smooth?

to enable Pete to go as fast as possible

to make it shiny

to make Pete go slowly

• Question 1

Choose the best word to complete this sentence:

Friction occurs between...

surfaces
EDDIE SAYS
Yes, when two surfaces (or even something like a plane and the air) come into contact, the force between them that determines how they move compared to each other .... that's friction.
• Question 2

Now think about moving objects and what's going on with friction.

Choose the best phrase to complete this sentence: "When an object is moving, friction... "

slows it down
EDDIE SAYS
Think about that boy on his bike: the tyres are in contact with the path. That's two surfaces, rubbing over each other. That's going to slow the bike down. In fact that's what you want - imagine the bike on an icy pond....!
• Question 3

When friction occurs,  which form of energy do you think is produced?

heat
EDDIE SAYS
Try this: rub your hands together, quite quickly. What do you feel? Yes, warmth. When two surfaces move over each other, heat is produced. That's because there is a frictional force between the two surfaces that are rubbing against each other and so they warm up. Check your car or bike's tyres after they've been out for a run - they'll feel warm.
• Question 4

Which THREE of these activities produce heat due to friction?

rubbing hands together
applying the brakes
rubbing two sticks together
EDDIE SAYS
We rub our hands together to create heat when we are cold!
We can make fire by rubbing sticks together very vigorously, but it's hard work. The amount of heat created by the friction can be so great that the wood begins to burn. Next time you're out on your bike, check how warm the brakes feel when you get back - lots of heat from friction there! Oh, and the Sun and gas oven - lots of heat there, but not due to friction.
• Question 5

When ROUGH surfaces rub together, the amount of friction created is...

large
EDDIE SAYS
The rougher the surfaces, the larger the friction between them. That's because they're bumpy and so it's harder for them to move over each other (try sliding a book across the table and across a carpet - see the difference?). Rougher surfaces = more friction.
• Question 6

Below are five objects which will move over another surface (like the ground).

Which THREE of these examples produces a large amount of friction?

knobbly tyres
walking boots
sand paper
EDDIE SAYS
So, knobbly tyres on a mountain bike, 'grippy' soles on a walking boot and sandpaper for rubbing down wood to make it smooth. Rough surfaces produce large amounts of friction when they rub together. Designers use this science when they are making all kinds of products. Ice skates and skis are designed to minimise friction and so help the person wearing them to go fast.
• Question 7

Pete has a new skateboard.  He notices that the grip-tape on top of the deck is rough.

This is to create...

high friction
EDDIE SAYS
The rough surface of the deck makes it a high friction surface and prevents him slipping off when he's doing his tricks!
• Question 8

Pete applies a force to the wheels of his skateboard. He notices that they spin for a long time.

This is due to...

low friction
EDDIE SAYS
So, inside the wheels of the skateboard are loads of tiny metal balls, called ball-bearings. What they do is to reduce the amount of friction between the wheel and the axle. Skateboarders want to go fast, so they want their wheels to whizz round quickly - that needs low friction. Right?
• Question 9

Which TWO reasons explain the need for low friction on this part of the skateboard?

to make it easy to start moving
to keep it moving
EDDIE SAYS
A skateboarder is keen to get their board moving fast. That means low friction in the wheels: easy to push off and then easy to keep it rolling, without too many foot pushes on the path.
• Question 10

At the skate park, Pete skates on the half-pipe.

Why do you think the surface of the half-pipe is smooth?

to enable Pete to go as fast as possible
EDDIE SAYS
As you know by now, the smooth surface is there to reduce friction and help skaters get maximum speed so that they can do tricks. True, it can look shiny too, but that doesn't really matter to the motion of the board - it's that low friction they want!
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