P6 General Studies | Forces and Simple Machines Lesson-Prep Guide (for tutors) | 45 minutes from friction to pulleys and gears

2026-11-08

Tutor lesson-prep guides · Primary General Studies

Students push and pull happily in experiments, yet asked which way friction points they answer the opposite way. This lesson sets one rule: fix where the force is and which way it acts, then look at what the machine gives you.

Objectives — Students can: (1) state that friction acts against motion and give two ways to reduce it; (2) label the fulcrum, effort and load on a lever diagram and sort levers into three classes; (3) distinguish a fixed pulley (changes direction, no saving in force) from a movable pulley (saves force, does not change direction); (4) explain that meshed gears turn in opposite directions and that a larger gear turns more slowly.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Describing direction	Push a box left – which way is friction	Right, against the motion
Measuring and comparing	How to compare two pulls	Same spring balance, same distance
Diagram habits	What a labelled point needs	A name for each point, not just an arrow
Observing gears	Two gears meshed together	One turns clockwise, the other anticlockwise

02 Lesson flow (45 minutes)

Time	Stage	Tutor does	Student does
0–8 min	Starter: push a box	Push a book across a desk, then across a towel	Says the towel is harder to push
8–17 min	Friction	Pull the book with a spring balance on a desk and on sandpaper	States the direction of friction and how to reduce it
17–26 min	Three lever points	Seesaw with a ruler and eraser; move the fulcrum	Labels the three points and explains each
26–35 min	Three lever classes	Scissors, bottle opener and tweezers	Sorts them and gives the reason
35–43 min	Pulleys and gears	Lift a load with a fixed then a movable pulley; mesh two gears	Explains direction change versus force saving
43–45 min	Exit check	Three quick oral questions	Answers independently

03 Teaching script (read it out)

Scene 1: Friction always opposes motion

The most common error is drawing friction the same way as the push. Give one checkable rule: friction always grabs you and stops you sliding. Show two cases: a box pushed forward has friction backwards; a box about to slide down a ramp has friction up the slope.
Only then list three ways to reduce it: add lubricant, use rollers or bearings, smooth the surfaces. Ask for one real object per method so the idea lands.

Student does: draws the push and the friction arrow, which must point opposite ways.

Scene 2: Name the three points before naming the class

Students judge a lever by its shape, so scissors and tweezers both get called “a lever” with no difference. The rule is to label first: fulcrum (the fixed pivot), effort (where the hand pushes), load (what has to move).
The class depends only on which point sits in the middle: fulcrum in the middle is class one (scissors, seesaw); load in the middle is class two (bottle opener, wheelbarrow); effort in the middle is class three (tweezers, fishing rod). Move the fulcrum along a ruler once and students see at once that the closer the fulcrum to the load, the easier the lift.

Student says: which point is in the middle, then the class name.

Scene 3: Pulleys trade direction for force; gears only change direction

Students assume every pulley saves force. Lift the same load twice: a fixed pulley on the ceiling changes only the direction of the pull and the force equals the weight; a movable pulley travels with the load, splits it between two rope sections, and saves force without changing direction.
Gears are different again: meshed gears always turn opposite ways, and a large gear driving a small one gives speed but less force. The bicycle makes it concrete: big chainring to small sprocket is fast but hard work.

Student says: fixed changes direction, movable saves force, and meshed gears turn opposite ways.

04 Question types and worked steps

Type	Example	Steps	Answer
Friction direction	A book pushed right across a desk	Fix the motion first, then reverse it	Friction points left
Lever class	Scissors, bottle opener, tweezers	Label three points, find the middle one	Class one, class two, class three
Pulley effect	Fixed then movable pulley on one load	Compare direction and effort	Fixed changes direction; movable saves force
Gears	Gear A clockwise drives gear B	Neighbours run opposite	B anticlockwise, speed depends on teeth

Sanity check (teach this): Reasonableness checks: friction must oppose relative motion, never follow the push; any claim of saving force must say what is traded (a movable pulley trades a longer rope for a smaller force); lever class depends only on the middle point, never on shape; meshed gears always run opposite, and one gear train cannot show two turning the same way; every conclusion needs a measurement or an observation.

05 Independent practice (3 questions)

Question	Answer	What to watch
4 friction directions	Push, pull, ramp, rolling	Checks the arrows are not reversed
3 lever classes	Scissors, bottle opener, tweezers	Checks the three points are labelled first
2 pulley comparisons	Fixed versus movable	Checks what is traded for the saving

06 Common mistakes and what to say

Mistake	Student writes	Say this
Drawing friction with the motion	Arrow pointing the same way as the push	“Friction holds you back, so it always opposes motion. Imagine pressing your hand on the book.”
Thinking a movable pulley changes direction	“Both pulleys change direction”	“Changing direction is the fixed pulley; the movable one saves force and you pull twice the rope.”
Classifying levers by shape	“The long one must be class one”	“Do not look at the shape. Look at which point is in the middle: fulcrum, load or effort.”
Assuming a big gear is faster	“The big gear turns faster”	“A big gear turns slower but with more force; the small gear is the fast one, as on a bicycle.”

07 Homework (paper, section and question numbers)

P6 general studies paper (with answers) — Do the forces and machines questions
Primary General Studies chapter index — All chapters in the subject
Redo this chapter — Redraw three levers with their points and classes

08 Exit check (last 5 minutes)

Question	Answer	Decision
Direction of friction	Against motion	Answering “with it” means going back to the second stage
How many lever classes	Three, by the middle point	Answering two means going back to the third stage
Which pulley saves force	The movable one	Answering fixed means going back to the fourth stage
Meshed gears	They turn opposite ways	Answering same way means going back to the fifth stage

09 Tutor FAQ

Do P6 students need the moment formula?

No. The qualitative rule that a fulcrum nearer the load lifts more easily is enough; the formula belongs to secondary physics.

What if there is no pulley set?

Build one from a coat hanger, string and a cotton reel, or show direction change with a curtain cord and a clip; that is sufficient.

Is friction always bad?

A good prompt: walking, writing and holding chopsticks all need friction. We only want to remove the friction we do not need, such as in bearings.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.