AQA A-level PE · Paper 2 · Biomechanical movement · Lever systems

FLE 123

Every movement is a lever: the fulcrum is the point the lever rotates about (usually the joint), the muscle gives the effort and the body part or object is the load. What sits in the middle decides the class. Drag F, E and L and watch.

Lever class3rdeffort in the middle
Effort arm0cm · fulcrum to effort
Load arm0cm · fulcrum to load
EA ÷ LA0mechanical advantage
Effort needed0N to hold the load

Drag the F, E and L markers along the 1 m bar, or use the sliders. Forces are drawn at right angles to the bar, so each arm is the perpendicular distance from the fulcrum. Bones are simplified to straight, rigid bars.

3rd classMechanical disadvantagePress Lift it to compare how far each end moves.
Try:
Lever mission 1/6Completed 0

Build a 2nd class lever.

Move the pieces until the mission is complete.

The body, drawn as a lever

Same joint. Same lever.

Left: the joint in action. Right: the same thing as an exam lever diagram, with F, E and L in the same order. Pick a joint, then load it into the builder.

01 · AQA definitions

Learn these word for word

Fulcrum
The point about which the lever rotates. In the body this is the joint.
Effort
The force applied by the user of the lever system. In the body this is the muscle (agonist).
Load
The resistance moved by the lever system. For example the weight of the body part, the body or an object being held.
Effort arm
The shortest perpendicular distance between the fulcrum and the application of effort.
Load arm
The shortest perpendicular distance between the fulcrum and the load.
Mech. advantage
The effort arm is longer than the load arm. A large load can be moved with a relatively small effort. Second class levers always have a mechanical advantage.
Mech. disadvantage
The load arm is longer than the effort arm. More effort is needed to move the load, but the lever has a large range of movement and can move the load quickly. Third class levers always have a mechanical disadvantage.

Why the arms matter. The builder balances the load using effort × effort arm = load × load arm. So the longer the effort arm compared with the load arm, the less effort you need. You don't need this equation in the exam, but it shows why a longer effort arm gives a mechanical advantage.

02 · The three classes

FLE 123

Ask one question: what is in the middle?

Fin the middle
1st class
Lin the middle
2nd class
Ein the middle
3rd class
ClassIn the middleExample in the bodyArmsWhat it gives
1stFulcrumExtension of the neck (tilting the head back); extension of the elbow (triceps)Either can be longerMechanical advantage or disadvantage, depending on where the fulcrum sits
2ndLoadPlantar flexion at the ankle (going up onto the toes, take-off)Effort arm longerMechanical advantage: large loads moved with little effort. But slower, with a smaller range of movement
3rdEffortFlexion of the elbow (biceps); knee extension; hip flexion. Most joints in the bodyLoad arm longerMechanical disadvantage: needs more effort. But a large range of movement and speed of movement
03 · Challenge

Name that lever

Six sporting actions, in a random order. For each one, name the class, then match the numbered points to the fulcrum, effort and load. Then decide: mechanical advantage or disadvantage? Three marks per action.

Action 1/6Score 0/18

–

Part 1: which class of lever?

04 · Exam diagrams

Getting the drawing marks

  1. Draw a straight line for the lever (the bone).
  2. Put a triangle under it for the fulcrum (the joint).
  3. Draw an arrow for the effort (the muscle) and an arrow for the load (the weight), in the correct order for the class.
  4. Label F, E and L, and name them for the action: e.g. F = elbow joint, E = biceps, L = weight of the forearm and dumbbell.
  5. If asked, mark the effort arm (fulcrum to effort) and load arm (fulcrum to load) and show which is longer.

Common slips. Measuring the arms to the end of the bone instead of to the effort and load. Calling third class levers simply "weak": they trade force for range and speed of movement. Muddling the order: always check what is in the middle. And the classic one: at the ankle the fulcrum is the ball of the foot, not the ankle joint.

05 · Exam practice

Try, then check

Question 1 · Identify3 marks

Identify the fulcrum, effort and load during the upward phase of a bicep curl.

Show mark scheme
  • Fulcrum: elbow (joint)
  • Effort: biceps (brachii)
  • Load: weight of the forearm/hand and the dumbbell
Question 2 · Draw and label4 marks

Draw and label the lever system operating at the ankle as a sprinter drives up onto the toes. Mark the effort arm and the load arm.

Show mark scheme
  • Fulcrum at one end: ball of the foot / metatarsals
  • Load in the middle: body weight (acting through the ankle/tibia)
  • Effort at the other end: gastrocnemius (via the Achilles tendon) pulling up on the heel
  • Effort arm (fulcrum to effort) and load arm (fulcrum to load) labelled, with the effort arm longer than the load arm
Question 3 · Classify2 marks

Name the class of lever operating at the neck when a footballer tilts their head back to look up at a high ball. Justify your answer.

Show mark scheme
  • First class lever
  • The fulcrum (joint between skull and atlas / top of the neck) is between the effort (neck extensors, e.g. splenius) and the load (weight of the head)
Question 4 · Apply3 marks

A performer holds a dumbbell in the hand with the elbow flexed. The biceps attach about 4 cm from the elbow joint; the dumbbell is about 35 cm from the elbow joint. Name the class of lever and state whether it has a mechanical advantage or a mechanical disadvantage. Justify your answer.

Show mark scheme
  • Third class lever
  • The effort (biceps) is between the fulcrum (elbow) and the load (dumbbell/forearm)
  • Mechanical disadvantage, because the load arm (35 cm) is longer than the effort arm (4 cm)

Extension (not needed for AQA marks): to hold the dumbbell the biceps must pull with about 35 ÷ 4 ≈ 8.75 times its weight.

Question 5 · Explain3 marks

Explain how the lever system at the knee benefits a footballer taking a long-range shot.

Show mark scheme
  • Third class lever: the effort (quadriceps via the patellar tendon) is between the fulcrum (knee) and the load (lower leg and foot)
  • The load arm is longer than the effort arm, which gives a large range of movement
  • So the foot moves quickly / with high speed, giving a greater velocity to the ball
Question 6 · Explain with examples6 marks

Using examples from sport, explain mechanical advantage and mechanical disadvantage in lever systems.

Show mark scheme
  • Mechanical advantage: the effort arm is longer than the load arm
  • A large load can be moved with a relatively small effort
  • Second class levers always have a mechanical advantage, e.g. plantar flexion at the ankle when driving off the blocks or taking off for a jump
  • Drawback of second class levers: slower, with a smaller range of movement
  • Mechanical disadvantage: the load arm is longer than the effort arm, so more effort is needed to move the load
  • But third class levers give a large range of movement and speed of movement, e.g. elbow flexion in a bicep curl, hip flexion when sprinting, knee extension when kicking
  • First class levers can give either, depending on where the fulcrum sits (e.g. neck extension, elbow extension)
  • Max 6 marks. Examples must be linked to the correct class to be credited.