PhysicsICSE Class 10 · Machines

Levers and Their Classes: Principle, Examples, Human Body Levers and MA (ICSE Class 10)

Q: How do I tell the class of a lever quickly?

Find what lies in the middle of the three points. Fulcrum in the middle is class I, load in the middle is class II, and effort in the middle is class III.

Q: Why do we use class III levers if their MA is less than 1?

They make the load move farther and faster than the effort, and they give reach or convenience, as with fire tongs, a fishing rod and the forearm.

Q: Is the MA of a lever equal to its VR?

For a light, frictionless lever both equal effort arm ÷ load arm. A real lever's own weight and friction at the fulcrum make its MA slightly less than its VR.

Updated 15 October 2026 · Fact-checked

A lever is a rigid bar turning about a fixed fulcrum. By the principle of moments, load × load arm = effort × effort arm, so MA = effort arm ÷ load arm. Class I has the fulcrum in the middle, class II the load (MA > 1) and class III the effort (MA < 1).

Understand Levers and Their Classes

A lever is a rigid bar, straight or bent, that can turn about a fixed point called the fulcrum (F). A load (L) acts at one point of the bar and an effort (E) at another.

Load arm: the perpendicular distance of the load's line of action from the fulcrum.
Effort arm: the perpendicular distance of the effort's line of action from the fulcrum.

Both arms are measured from the fulcrum, not from the ends of the bar.

Principle of the lever. When the lever is in equilibrium, the moment of the effort about the fulcrum balances the moment of the load (principle of moments):

$E \times effort arm = L \times load arm .$

So, for an ideal lever,

$M A = \frac{L}{E} = \frac{effort arm}{load arm} .$

When the lever turns through a small angle, each point moves a distance proportional to its distance from the fulcrum, so $V R = \frac{d _{E}}{d _{L}} = \frac{effort arm}{load arm}$ too. For a light, frictionless lever MA = VR; a real lever's weight and the friction at the fulcrum make its MA slightly less.

The three classes depend only on what lies in the middle.

Class I: fulcrum in the middle (L F E). The fulcrum lies between the load and the effort. The effort arm can be longer than, equal to or shorter than the load arm, so MA > 1, = 1 or < 1. Examples: see-saw, crowbar, claw hammer pulling a nail, scissors, pliers, beam balance (MA = 1), handle of a hand pump.

Class II: load in the middle (F L E). The load lies between the fulcrum and the effort, so the effort arm is always longer than the load arm: MA > 1 always. These levers are force multipliers. Examples: nutcracker, wheelbarrow, bottle opener, lemon squeezer, paper cutter.

Class III: effort in the middle (F E L). The effort acts between the fulcrum and the load, so the effort arm is always shorter: MA < 1 always. More effort is needed than the load, but the load moves farther and faster than the effort. Examples: fire tongs, sugar tongs, fishing rod, the human forearm.

Levers in the human body (named in the syllabus):

Class I: nodding the head. The fulcrum is the joint at the top of the spine; the weight of the head acts in front of it; the neck muscles at the back provide the effort.
Class II: standing on tiptoe. The fulcrum is at the ball of the foot (the toes); the body's weight acts through the ankle in the middle; the calf muscles pull up at the heel through the Achilles tendon.
Class III: lifting a load in the hand with the forearm. The fulcrum is the elbow; the biceps muscle pulls upward a few centimetres from the elbow; the load is in the palm, much farther away.

The same job, different classes. Cutting can be done with scissors (class I) or a paper cutter (class II); holding can be done with pliers (class I) or tongs (class III). The class is decided by positions, not by the job.

A shortcut. Remember 'F, L, E in the middle for I, II, III'. Then MA > 1 is guaranteed only for class II and MA < 1 only for class III.

Levers and Their Classes: formulas and key facts

Principle of the lever: $E \times effort arm = L \times load arm$; Arms measured perpendicularly from the fulcrum.
MA of a lever: $M A = \frac{L}{E} = \frac{effort arm}{load arm}$; For a light, frictionless lever, VR has the same value.
Class and MA: $I: M A ≷ 1; II: M A > 1; III: M A < 1$; Class I can have MA greater than, equal to or less than 1.

How to solve Levers and Their Classes questions

Every lever question needs the fulcrum found first; everything else is measured from it.

1Make a rough sketch: mark F, L and E at their real positions on the bar.
2Name the class from what is in the middle: F (I), L (II), E (III).
3Measure the load arm and the effort arm from the fulcrum, in the same unit.
4Use $E \times effort arm = L \times load arm$ to find the unknown force or distance.
5Find $M A = \frac{effort arm}{load arm}$ (or $\frac{L}{E}$ ) and check it agrees with the class.

Levers and Their Classes in real life

Each concept, met in an everyday situation. Read the situation, try the problem, then check the solution. The one-line hook is what to remember.

A claw hammer as a class I lever

Suppose you pull out a nail with a claw hammer. The head rests on the wood and acts as the fulcrum; the nail is gripped 5 cm from it, and you pull the handle 30 cm from it. The nail resists with a force of 1800 N.

Find the effort needed and the MA.

Try it first, then show the solutionSolution

$E \times 30 = 1800 \times 5$ , so $E = 300$ N.
$M A = \frac{30}{5} = 6$ .

Answer: 300 N; MA = 6.

Memory hook: Long handle, short claw: the fulcrum sits close to the load.

Opening a paint tin

Imagine you lever up the lid of a paint tin with a screwdriver. The tip is under the lid 0.5 cm from the rim, which acts as the fulcrum, and your hand pushes down 20 cm from the rim. The lid needs 200 N to lift.

Name the class of lever and find the effort.

Try it first, then show the solutionSolution

The rim (fulcrum) is between the lid (load) and the hand (effort): class I.
$E = \frac{200 \times 0.5}{20} = 5$ N; $M A = 40$ .

Answer: Class I; only 5 N of effort.

Memory hook: Put the fulcrum as close to the load as you can.

Tricks to remember Levers and Their Classes

Short memory aids. Say each one aloud once, then use it on a question the same day.

F-L-E in the middle
Class I, II, III have F, L, E in the middle, in that order: 'FLE 1-2-3'.
Use it when: Naming the class from a sketch.
Two is too strong, three is free speed
Class II always multiplies force (MA > 1); class III always gains speed and distance (MA < 1).
Use it when: MA statements and assertion–reason questions.
Body levers: nod, tiptoe, lift
Nod (I), tiptoe (II), lift with the forearm (III): the order you would do them waking up.
Use it when: Human body examples.
Arms start at F
Every arm begins at the fulcrum, like the hands of a clock start at the centre.
Use it when: Avoiding arms measured from the end of the bar.

Levers and Their Classes: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Class and MA of a bottle opener · 1 mark · MCQBoard level

A bottle opener is a lever of:
(a) class I, with MA less than 1
(b) class II, with MA greater than 1
(c) class III, with MA less than 1
(d) class II, with MA less than 1

Try it first, then show the solutionSolution

The fulcrum is at the top edge of the cap, the effort at the far end of the handle, and the load (the grip of the cap) lies between them: class II.
Class II always has effort arm > load arm, so MA > 1.

Answer: (b) class II, with MA greater than 1

Example 2: Moving a stone with a crowbar · 3 marks · Short answerBoard level

A crowbar rests on a small block that acts as the fulcrum. A stone presses on one end of the bar 0.2 m from the block, and a worker pushes the other end 1.0 m from the block. The stone needs a force of 900 N to move. Find (a) the class of lever, (b) the effort needed, (c) the MA.

Try it first, then show the solutionSolution

(a) The fulcrum is between the load and the effort: class I. (1)
(b) $E \times 1.0 = 900 \times 0.2$ , so $E = 180$ N. (1)
(c) $M A = \frac{1.0}{0.2} = 5$ . (1)

Answer: (a) Class I (b) 180 N (c) 5

Example 3: A loaded wheelbarrow · 3 marks · Short answerHarder board level

A wheelbarrow and its sand weigh 600 N in total, acting at a point 0.4 m from the axle of the wheel. The gardener lifts the handles at 1.5 m from the axle. (a) Name the class of lever. (b) Find the upward force needed at the handles. (c) Find the MA.

Try it first, then show the solutionSolution

(a) Fulcrum at the axle, load in the middle, effort at the handles: class II. (1)
(b) $E \times 1.5 = 600 \times 0.4$ , so $E = 160$ N. (1)
(c) $M A = \frac{600}{160} = 3.75$ . (1)

Answer: (a) Class II (b) 160 N (c) 3.75

Example 4: Three levers of equal length · 3 marks · Short answerHarder board level

Three bars X, Y and Z, each 1 m long, are used as levers with the load at one end and the effort at the other. The fulcrum is 0.2 m from the load end in X, 0.5 m in Y and 0.8 m in Z. (a) Name the class of all three. (b) Find the MA of each. (c) Which needs the least effort, and what effort does Z need for a 100 N load?

Try it first, then show the solutionSolution

(a) In each, the fulcrum is between the load and the effort: all are class I. (½)
(b) X: $M A = \frac{0.8}{0.2} = 4$ ; Y: $\frac{0.5}{0.5} = 1$ ; Z: $\frac{0.2}{0.8} = 0.25$ . (1½)
(c) X needs the least effort (largest MA). For Z: $E \times 0.2 = 100 \times 0.8$ , so $E = 400$ N. (1)

Answer: (a) All class I (b) 4, 1, 0.25 (c) X; 400 N

Example 5: Standing on tiptoe · 3 marks · Short answerHarder board level

A person of weight 600 N stands on the toes of one foot. Take the fulcrum at the ball of the foot. The weight acts through the ankle, 0.12 m from the fulcrum, and the calf muscle pulls up at the heel, 0.16 m from the fulcrum. (a) Name the class of lever. (b) Find the force exerted by the calf muscle. (c) Find the MA.

Try it first, then show the solutionSolution

(a) Load (at the ankle) between fulcrum and effort: class II. (1)
(b) $E \times 0.16 = 600 \times 0.12$ , so $E = 450$ N. (1)
(c) $M A = \frac{0.16}{0.12} \approx 1.33$ . (1)

Answer: (a) Class II (b) 450 N (c) About 1.33

Example 6: Case study: pruning shears · 4 marks · Case-basedHOTS / competency

A gardener's shears pivot at a hinge. A twig needs a cutting force of 400 N. The gardener's hand presses the handles 30 cm from the hinge.
(a) Name the class of lever.
(b) Find the effort if the twig is cut 8 cm from the hinge, near the tips.
(c) Find the effort if it is cut 3 cm from the hinge.
(d) Use your answers to explain why gardeners push a thick twig deep into the jaws, and why shears for metal have short blades and long handles.

Try it first, then show the solutionSolution

(a) Hinge between blade and handle: class I. (½)
(b) $E = \frac{400 \times 8}{30} \approx 107$ N (MA = 3.75). (1)
(c) $E = \frac{400 \times 3}{30} = 40$ N (MA = 10). (1)
(d) A twig deep in the jaws has a short load arm, so the MA is larger and less effort is needed. Metal needs a large force, so a short load arm (short blades) and a long effort arm (long handles) give a large MA. (1½)

Answer: (a) Class I (b) About 107 N (c) 40 N (d) Shorter load arm, larger MA, smaller effort.

Where students lose marks in Levers and Their Classes

The slips examiners see most often, and what to write instead.

Mistake: Classifying by memory instead of by position
The class depends on what lies in the middle, which a sketch shows at once.
Wrong working
'Scissors cut, so they are class II like a paper cutter.'
Right working
Scissors: rivet (fulcrum) in the middle, so class I.
Do this: Draw a quick line with F, L and E marked before answering.
Usually costs: CISCE examiners noted for 2024 Q1(vii) that the classes were unclear and that some candidates added wrong, unasked diagrams.
Mistake: Judging MA by the effort arm alone
MA is the ratio of the effort arm to the load arm of the same lever.
Wrong working
'Lever Z has the longest effort arm, so it has the largest MA,' without looking at its load arm.
Right working
Compare $\frac{effort arm}{load arm}$ for each lever.
Do this: Write the ratio for every lever before comparing.
Usually costs: Reported for 2025 Q6(ii), where candidates also failed to say all three levers were class I.
Mistake: Measuring arms from the end of the bar
Both arms start at the fulcrum.
Wrong working
Bar 1 m, fulcrum 0.25 m from the load end: $M A = \frac{1}{0.25} = 4$ .
Right working
Effort arm $= 1 - 0.25 = 0.75$ m, so $M A = \frac{0.75}{0.25} = 3$ .
Do this: Subtract to find each arm from F.
Usually costs: The method and answer marks.
Mistake: Saying every class I lever has MA > 1
In class I the fulcrum can be anywhere between L and E.
Wrong working
'A beam balance is class I, so its MA is more than 1.'
Right working
Equal arms give MA = 1; a fulcrum nearer the effort gives MA < 1.
Do this: Only class II (always > 1) and class III (always < 1) are fixed.
Usually costs: Assertion–reason and MCQ marks.

Exam tips

Support every classification with a small sketch marking F, L and E, as the CISCE examiners advise, but draw only what is asked.
For 'why is MA of class II always more than 1?', answer in terms of arms: the load lies between F and E, so the effort arm is always longer than the load arm.
When comparing levers, write the MA of each as effort arm ÷ load arm; one line per lever earns the marks.
Learn one human body example for each class with its F, L and E named.

Practice questions on Levers and Their Classes

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which pair are both class III levers?
(a) fire tongs and a fishing rod
(b) scissors and a nutcracker
(c) a wheelbarrow and the human forearm
(d) a see-saw and a bottle opener
Hint
Look for the effort in the middle.
Answer
(a) fire tongs and a fishing rod
Q2 · 3 marks · Short answerBoard level
State the class of lever, and say what lies in the middle, for (a) a lemon squeezer, (b) a pair of pliers, (c) a fishing rod.
Hint
Sketch each and mark F, L and E.
Answer
(a) Class II: load (the lemon) in the middle. (b) Class I: fulcrum (the rivet) in the middle. (c) Class III: effort (the front hand) in the middle.
Q3 · 2 marks · Short answerHOTS / competency
A student says, 'Class III levers are useless because their MA is less than 1.' Give two reasons, with an example of each, why this is wrong.
Hint
What does a class III lever gain?
Answer
(1) The load moves farther and faster than the effort: the forearm moves the hand through a large distance for a small contraction of the biceps. (2) It gives reach and convenience: fire tongs or sugar tongs keep the hand away from hot or clean objects.
Q4 · 2 marks · Short answerHarder board level
A bottle opener is 10 cm long from the fulcrum to where the hand pushes. The opener grips the cap 1.2 cm from the fulcrum, and the cap needs 150 N to lift. Find the effort and the MA.
Hint
$E \times effort arm = L \times load arm$ .
Answer
$E = \frac{150 \times 1.2}{10} = 18$ N; $M A = \frac{150}{18} \approx 8.3$ .
Q5 · 3 marks · Short answerHarder board level
With the forearm horizontal, a 50 N ball is held in the palm 35 cm from the elbow. The biceps pulls up 5 cm from the elbow. (a) Find the force in the biceps. (b) Find the MA. (c) If the biceps shortens by 1 cm, how far does the ball rise?
Hint
Class III: effort arm 5 cm, load arm 35 cm.
Answer
(a) $E = \frac{50 \times 35}{5} = 350$ N. (b) $M A = \frac{5}{35} = \frac{1}{7} \approx 0.14$ . (c) $1 \times \frac{35}{5} = 7$ cm.
Q6 · 2 marks · Short answerHarder board level
When the head is held level, its weight of 50 N acts 2.5 cm in front of the joint at the top of the spine, and the neck muscles pull down 5 cm behind the joint. (a) Name the class of lever. (b) Find the force in the neck muscles and the MA.
Hint
The joint is between the load and the effort.
Answer
(a) Class I. (b) $E = \frac{50 \times 2.5}{5} = 25$ N; $M A = \frac{5}{2.5} = 2$ .
Q7 · 4 marks · Long answerHOTS / competency
A light rigid bar 2 m long is to be used to raise a 1200 N load with an effort of 200 N, the effort being applied at one end. (a) If it is used as a class I lever with the load at the other end, where must the fulcrum be? (b) If instead it is used as a class II lever with the fulcrum at the other end, where must the load be placed? (c) Why can it never do this job as a class III lever?
Hint
You need MA = 6. In (a) the two arms add up to 2 m.
Answer
MA needed $= \frac{1200}{200} = 6$ . (a) Effort arm $= 6 \times$ load arm and the two add to 2 m, so the load arm $= \frac{2}{7} \approx 0.29$ m: the fulcrum is about 0.29 m from the load end. (b) Effort arm = 2 m, so load arm $= \frac{2}{6} \approx 0.33$ m from the fulcrum. (c) A class III lever always has MA < 1, so the effort would have to exceed 1200 N.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Class of a see-saw?Show answer
Class I.
2.MA of a class II lever is always…?Show answer
Greater than 1.
3.Class of the human forearm lifting a load?Show answer
Class III.
4.Where is the fulcrum when you stand on tiptoe?Show answer
At the ball of the foot (the toes).
5.MA of a lever with effort arm 60 cm and load arm 15 cm?Show answer
4.

Levers and Their Classes: frequently asked questions

How do I tell the class of a lever quickly?

Find what lies in the middle of the three points. Fulcrum in the middle is class I, load in the middle is class II, and effort in the middle is class III.

Why do we use class III levers if their MA is less than 1?

They make the load move farther and faster than the effort, and they give reach or convenience, as with fire tongs, a fishing rod and the forearm.

Is the MA of a lever equal to its VR?

For a light, frictionless lever both equal effort arm ÷ load arm. A real lever's own weight and friction at the fulcrum make its MA slightly less than its VR.