Friction: friend and enemy

Lesson overviewGROW · Week 3

Friction: friend and enemy

One force. Different jobs.

Explain what friction does, and when it helps or hinders.

FORCES / CONTACT / EVIDENCE

Contextual illustration of a wooden block beside a textured surface. It is not a recorded experimental result.

Friction: friend and enemySlide 1 of 12

You Do · practiseGROW · Week 3

What do you notice?

Supported: gently rub your hands for five seconds.

Standard: describe what you feel and name the force.

Stretch: explain where the warmth came from.

You can watch, point, speak, draw or write.

Friction: friend and enemySlide 2 of 12

I Do · learn and modelGROW · Week 3

Three things to work out

1 What is friction?

2 When does friction help or hinder?

3 What will happen on two different surfaces?

Friction: friend and enemySlide 3 of 12

I Do · learn and modelGROW · Week 3

Friction acts at a contact

Read the slide text

The block slides right on a horizontal surface. The sliding arrow points right; friction on the block points left. BLOCK sliding right friction on the block A force between surfaces that slide, or try to slide, past each other. Name the two touching surfaces.

Friction: friend and enemySlide 4 of 12

I Do · learn and modelGROW · Week 3

Change one thing: the surface

Read the slide text

A block slides right while friction at its surface contact points left. Only the run-out surface is changed in the proposed comparison. Keep the block, ramp and release the same. Change only the run-out surface. Predict where the block will stop. Then observe. What stayed the same? What changed? BLOCK sliding friction surface contact

Friction: friend and enemySlide 5 of 12

We Do · think togetherGROW · Week 3

Helpful or unhelpful?

Bike brakes

Trainers on a wet floor

Moving engine parts rubbing

Pushing a heavy box across carpet

A door handle

Name the surfaces. Explain the job.

Friction: friend and enemySlide 6 of 12

We Do · think togetherGROW · Week 3

The job changes the answer

HELPS THE JOB	HINDERS THE JOB
Braking a wheel Gripping the floor Holding a handle	Moving parts heating and wearing Sliding a box across carpet

Friction: friend and enemySlide 7 of 12

I Do · learn and modelGROW · Week 3

Explain both sides

Friction is helpful here because…

…but it is unhelpful here because…

Use the touching surfaces and the job in your explanation.

Friction: friend and enemySlide 8 of 12

We Do · think togetherGROW · Week 3

Sort the claims

TRUE / FALSE / NOT A SCIENTIFIC CLAIM

Sliding friction opposes sliding at the contact.

Friction only happens with rough surfaces.

Oil can reduce friction in suitable lubricated contacts.

Without friction we could not walk normally.

Friction is a bad force.

Friction: friend and enemySlide 9 of 12

We Do · think togetherGROW · Week 3

Check the science

Your response

Keep your first choices, then reveal the check.

Reveal the model

TRUE Sliding friction opposes sliding at the contact.

FALSE Smooth surfaces can have friction too.

TRUE Suitable lubrication can reduce friction.

TRUE Walking normally needs grip at the ground.

JUDGEMENT “Bad” depends on the job.

Friction: friend and enemySlide 10 of 12

We Do · think togetherGROW · Week 3

Build a complete explanation

Read the slide text

A downward arrow connects movement energy to heat, illustrating energy transfer by friction. Friction is helpful at a bike brake: it transfers movement energy to heat and slows the wheel. It can be unhelpful between moving engine parts because rubbing heats and wears them. MOVEMENT ENERGY HEAT

Friction: friend and enemySlide 11 of 12

We Do · think togetherGROW · Week 3

Keep your prediction for next time

Keep your named worksheet and first prediction.

Next lesson: compare three surfaces and repeated results.

Point to one idea you want to check again.

Friction: friend and enemySlide 12 of 12

Use the controls or left and right arrow keys. Printing includes pupil content; model answers remain separate.