Four Scenarios
Block on Slope — single block; explores forces parallel and perpendicular to a slope.
Ladder — ladder against a wall with a person on it; moments and friction at the base.
Hinged Rod — horizontal rod hinged at one end, held by a strut; tension and hinge reaction.
Hinged Door — vertical door on two hinges; weight distribution between upper and lower hinges.
Common Gestures (All Scenarios)
Drag the slope, wall, ladder ends, person, hinges, or rod endpoints directly on the canvas.
Click / tap a force vector to lock its value display on; click again to hide.
Drag labels (W, R, F, T, etc.) to reposition them.
Drag the triangle-of-forces panel to move it where you want.
Double-click / double-tap a moved label or panel to return it to its default position.
Block on Slope
Use the calculation-method tickbox to switch between the two ways of resolving W: along the slope or vertically.
F is the friction force, drawn along the slope. R is the normal reaction, perpendicular to the slope.
Toggle Parallelogram to select up to two forces and see them combined head-to-tail.
The triangle of forces in the panel updates live as you change the slope angle.
Ladder
Move the person up and down the ladder by dragging.
Take moments about the base to find the wall reaction (no friction at the wall).
Vertical equilibrium gives the normal reaction at the base; horizontal gives the friction needed.
If required friction exceeds μR, the ladder slips — shown by the warning.
Hinged Rod
Drag the load along the rod, or drag the strut anchor (D) on the wall.
Tension T acts along the strut. Hinge reaction R at A balances the rest.
Toggle Show tension components to resolve T into T_x and T_y at the strut's upper end.
Toggle Show hinge components for the corresponding decomposition of R at A.
Hinged Door
Drag the door's edges to change width/height; drag the CoG marker to move the centre of gravity.
Drag either hinge to adjust its position along the door's vertical edge.
Top hinge typically pulls outwards; bottom hinge pushes inwards — together they provide a couple to balance the weight's moment.
Their vertical components share the weight; total vertical reaction = door weight.