MYP Physics: Simple Machines & Levers FAQ

Simple machines are devices — levers, pulleys, inclined planes, wheels and axles — that change the size or direction of a force to make work easier. A lever is a rigid bar pivoting on a fixed point (the fulcrum), used to gain mechanical advantage so a smaller effort force can lift a larger load.

Class 1 levers have the fulcrum between the load and effort (a see-saw or scissors). Class 2 levers have the load between the fulcrum and effort (a wheelbarrow). Class 3 levers have the effort between the fulcrum and load (a fishing rod or your forearm lifting a weight).

Mechanical advantage (MA) equals load force divided by effort force, or equivalently the effort arm length divided by the load arm length. A longer effort arm relative to the load arm gives a higher MA, meaning less effort force is needed to move the same load.

Mechanical advantage compares load force to effort force — it tells you how much a machine multiplies force. Efficiency compares useful work output to total work input, expressed as a percentage, and it's always below 100% in real machines because friction wastes some energy as heat.

You need: MA = load ÷ effort (or effort arm ÷ load arm for levers); work done = force × distance; and efficiency = (useful output energy ÷ total input energy) × 100%. These three connect force, distance and energy transfer across every simple machine you'll study.

Simple machines is typically assessed against Criterion A (Knowing and Understanding) for calculations and definitions, and Criterion B (Inquiring and Designing) or Criterion C (Processing and Evaluating) if you're running a practical lever or pulley investigation with real measurements.

The most common command terms are 'calculate' (show full working for MA or efficiency), 'explain' (give reasons, e.g. why efficiency is under 100%), 'identify' (name the lever class or simple machine), and 'compare' (contrast two machines' mechanical advantage or use).

Focus on three things: knowing the three lever classes with a real example each, being fluent with the MA and efficiency formulas, and practising past-paper-style calculation questions until the working feels automatic rather than something you have to think through from scratch.

Not conceptually hard, but it's a topic where careless mistakes cost marks — mixing up load and effort arms, or forgetting units. Most students who struggle aren't confused by the idea of a lever; they're rushing the calculation and skipping a step in the working.

Because the fulcrum isn't always visually obvious — in a wheelbarrow, the wheel itself is the fulcrum, not the handles. The fix is to always identify where the object pivots first, then locate the load and effort relative to it, rather than guessing from the picture.

Simple machines lays the groundwork for DP Physics topics on work, energy and power, and for the mechanics unit's treatment of torque and equilibrium. Students who're comfortable with MA and efficiency calculations at MYP 4-5 find the DP energy-transfer questions far less intimidating.

This depends on your school's unit planner rather than a fixed IB requirement — the MYP doesn't mandate exact year placement for individual topics within Sciences. Most schools introduce simple machines and levers in MYP 4, then revisit force and energy concepts in more depth in MYP 5.

Past-paper-style practice questions with full worked solutions help more than re-reading a textbook chapter, because this topic is really a calculation skill dressed up as a concept. Look for graded questions that isolate the lever-class identification, then the MA calculation, then the efficiency calculation separately.