IB SEHS: Introduction to Forces in Sport

A force is a vector, meaning it has:

• Magnitude (how big it is)

• Direction (where it acts)

That single word “vector” helps you avoid vague exam lines like “more force means more movement.” In IB SEHS, you want cause and effect: a larger forward-directed force produces greater acceleration, or a braking force opposite to motion causes deceleration.

If you want the most exam-aligned wording and examples, RevisionDojo’s notes sequence for this unit is the fastest route: B.2 Notes.

Internal vs external forces in IB SEHS sport examples

Most IB SEHS exam questions are really asking you to sort forces into a simple story: what the athlete produces versus what the environment does back.

Internal forces

Internal forces are generated within the body, mainly by muscles pulling on bones to create movement at joints. Think of the quadriceps extending the knee during a jump take-off, or the biceps brachii contributing to elbow flexion during a lift.

If muscle roles trip you up, pair force content with this refresher: Agonist and antagonist muscles made simple.

External forces

External forces act on the body from outside. In sport, the big ones you see repeatedly in IB SEHS are:

• Gravity (always downward)

• Friction (opposes sliding between surfaces)

• Air resistance/drag (opposes motion through air)

• Contact forces (from the ground, equipment, opponents)

External forces are often the difference between a good technique and an injury mechanism. If you want an applied bridge to injury questions, this is a strong extension read: How forces cause injury.

How forces change motion (the exam-friendly phrasing)

In IB SEHS, forces affect motion in three high-yield ways:

• Initiating movement (overcoming inertia)

• Changing speed (acceleration or deceleration)

• Changing direction (changing velocity, even if speed stays constant)

A sprinter accelerates because they apply a backward force into the ground and receive a forward ground reaction force. A football changes direction because the athlete applies a sideways force, creating lateral acceleration. A landing slows the body because forces act opposite to motion, ideally spread over time by good technique.

To practise these explanations in the same style as exam questions, use RevisionDojo’s targeted practice: B.2 Forces, motion and movement Questionbank.

How to revise IB SEHS forces without memorising blindly

Forces can feel abstract until you attach them to scenarios. A good rhythm for IB SEHS revision is:

• Read one section of the syllabus-aligned hub: IB SEHS resources

• Turn definitions into spaced repetition using RevisionDojo Flashcards

• Ask RevisionDojo AI Chat to quiz you on “magnitude vs direction” with sport examples

• Use the Grading tools to check whether your explanation has a clear chain of cause and effect

• Finish with Mock Exams and Predicted Papers to apply under time pressure

If you like learning through bigger pictures, this biomechanics roadmap connects force to what comes next: Conquering Biomechanics: A Visual Guide to SEHS Topic 4.

Conclusion: Make IB SEHS forces feel automatic

Forces are the quiet engine under every sport highlight. In IB SEHS, your job is to describe that engine with calm precision: force as a vector, internal versus external forces, then a clear link to changes in motion.

If you want to turn that understanding into marks, build a simple loop with RevisionDojo: read the B.2 Forces, motion and movement notes, drill the Questionbank, and lock in definitions with Flashcards and AI Chat. Once forces start sounding “obvious” in your own words, you are very close to top-band IB SEHS answers.

IB SEHS goal setting in sport made simple: goal types, SMART targets, common mistakes, and exam-ready tips using RevisionDojo practice tools.