Free Body Diagrams
Aim: draw every force acting on the object, label it, and make the arrow lengths show whether the forces are balanced.
Drag out from the object to draw a force arrow. Click an arrow to select it, then choose its name. Drag an arrowhead to change its direction or length.
0 forces drawn
Name the selected force
Draw or select an arrow first.
Keyboard (focus the diagram): N new arrow, [ ] switch arrow, ← → rotate, ↑ ↓ resize, Delete remove.
Drawing a good free body diagram
- Draw only the forces acting on the object — not forces it exerts.
- Start each arrow at the object and point it the way the force acts.
- Longer arrow = bigger force. Equal and opposite arrows mean balanced forces.
- Balanced forces (resultant = 0): the object is at rest or moves at a steady speed in a straight line.
- Unbalanced forces: the object speeds up, slows down or changes direction, in the direction of the resultant force.
- Draw each force as its own arrow, even when two act in the same direction (e.g. friction and air resistance on a car). The resultant is what you get when you add them together.