MYP Physics: Forces & Free-Body Diagrams FAQ

A free-body diagram is a simplified sketch of one object, drawn as a dot or box, with arrows showing every force acting on it — each arrow starting at the object, pointing in the force's direction, with its length roughly showing relative size. No other objects, paths, or velocity arrows belong on it.

Balanced forces are equal in size and opposite in direction, so their resultant is zero and the object stays at rest or moves at constant velocity — this is Newton's first law. Unbalanced forces produce a non-zero resultant, which causes acceleration, per Newton's second law (F = ma).

Add forces acting in the same direction and subtract forces acting in opposite directions along the same line. For forces at right angles, use Pythagoras' theorem to find the resultant magnitude, then trigonometry (tan⁻¹) to find its direction relative to the original forces.

Newton's second law states that resultant force equals mass times acceleration (F = ma), where force is in newtons, mass in kilograms, and acceleration in metres per second squared. It links directly to free-body diagrams: once you've found the net force from the diagram, F = ma gives you the acceleration.

Forces and free-body diagrams are assessed mainly through MYP Criterion C (Processing and Evaluating) and Criterion D (Reflecting on the Impacts of Science), plus Criterion A (Knowing and Understanding) for identifying force types and applying Newton's laws in calculations and diagrams.

The biggest three: drawing forces that don't actually act on the object (like including a force from a second object in the diagram), forgetting weight entirely, and drawing arrow lengths that contradict the described motion (equal arrows when the object is accelerating).

Top-band work shows accurate diagrams, correct use of Newton's laws in calculations, and — critically for Criterion C and D — genuine evaluation of your own method's limitations, not just a stated conclusion. Students who reach the highest bands explain WHY friction or air resistance caused their result to differ from theory, with specific numbers.

Usually it's presentation, not physics — MYP Criterion A and C both reward showing your working with correct units at every step, not just a final number. A right answer with no formula shown, or with inconsistent units (mixing grams and kilograms), typically caps you well below the top achievement band.

MYP forces topics build the exact foundation DP Physics assumes on day one — Newton's laws, resultant force, and free-body diagrams reappear in DP Physics SL/HL Topic 2 (Mechanics), just with more complex scenarios like circular motion and momentum conservation. A shaky grasp here genuinely shows up in DP grades.

Not conceptually harder, but it's more common to lose marks here because it demands precise diagram conventions alongside the maths — unlike, say, energy topics, where a written explanation alone can carry most of the marks. Students who are strong at algebra but weak at spatial/diagram work often find this the trickier unit.

Look for resources with worked free-body diagram examples and MYP-criterion-aligned practice questions, not just general physics explanations — the diagram conventions and command terms (analyse, evaluate, justify) are specific to MYP assessment. On revisionprep.com, Revision Notes and Topical Worksheets for MYP Physics cover this exact structure.

Self-study resources like structured notes and worksheets typically cost far less than tutoring — often a one-off subscription fee rather than an hourly rate — and let your child practise free-body diagrams and force calculations at their own pace, which matters given how much this topic depends on repetition, not just explanation.

Yes, indirectly — MYP Criterion A and C results give a genuine early signal of whether your child finds mechanics-style physics intuitive, which is the strongest predictor of comfort in DP Physics SL or HL. A student who consistently struggles with force diagrams at MYP 4-5 is worth extra support before committing to DP Physics HL.