IB Physics HL A.2.3 Free-body Diagrams

Practise analysing HL free-body diagrams for coupled systems, buoyancy, orbital motion, drag, tension and changing force conditions.

Exam points

Construct and interpret diagrams for coupled forces, buoyancy, drag and tension.
Use free-body diagrams to model orbital, circular and non-uniform force situations.

[Maximum number: 2]

A girl on a sledge is moving down a snow slope at a uniform speed.

Figure for Question A.2.3—Free-body diagrams question 1 — IB Physics HL

Draw the free-body diagram for the sledge at the position shown on the snow slope.

arrow vertically downwards labelled weight «of sledge and/or girl»/W/mg/gravitational force/ $F_{\mathrm{g}} / F_{\text {gravitational }}$ AND arrow perpendicular to the snow slope labelled reaction force/R/normal contact force/N/ $F_{\mathrm{N}}$ friction force/F/f acting up slope «perpendicular to reaction force»

Do not allow G/g/"gravity".

Do not award MP1 if a "driving force" is included. Allow components of weight if correctly labelled. Ignore point of application or shape of object.

Ignore "air resistance". Ignore any reference to "push of feet on sledge".

Do not award MP2 for forces on sledge on horizontal ground

The arrows should contact the object

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A.2.3—Free-body diagrams question 1