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A simple experiment concerning the equilibrium of three forces is simulated here: Weights are suspended from three tied cords. Two of the cords run over frictionless pulleys. The three forces acting on the knot (coloured arrows) are in equilibrium. You can write forces from 1 N to 10 N into the text fields (don't forget to press the "Enter" key!). Notice that each force must be smaller than the sum of the other two forces! It is possible to vary the positions of the two pulleys by dragging the mouse. The parallelogram of the forces which are directed to the top left and right (red respectively blue) will be drawn if you select the corresponding option. At the bottom right you can read the angles of these two forces with respect to the vertical.

Downloadable Files

If your computer is set up with Geometers Sketchpad 4 then you can download this file to investigate equilibrium further.
Sketchpad - pend01Sketchpad - pend01
Investigate pendulums further using Geometer's Sketchpad

Software/Applets used on this page

JAOP
Based on free Java applets from Java Applets on Physics

Glossary

equilibrium

the state of an object when the vector sum of all forces acting on it is zero and when the algebraic sum of the moments of the forces about any point is zero

force

that which causes a body to accelerate or change in momentum

Full Glossary List

This question appears in the following syllabi:

SyllabusModuleSectionTopicExam Year
AQA A-Level (UK - Pre-2017)M1StaticsForces as vectors-
AQA A2 Maths 2017MechanicsEquilibrium and ResolvingResolving Forces-
AQA AS/A2 Maths 2017MechanicsEquilibrium and ResolvingResolving Forces-
CCEA A-Level (NI)M1StaticsForces as vectors-
CIE A-Level (UK)M1StaticsForces as vectors-
Edexcel A-Level (UK - Pre-2017)M1StaticsForces as vectors-
Edexcel A2 Maths 2017MechanicsResolving Forces and FrictionResolving Forces-
Edexcel AS/A2 Maths 2017MechanicsResolving Forces and FrictionResolving Forces-
OCR A-Level (UK - Pre-2017)M1StaticsForces as vectors-
OCR A2 Maths 2017MechanicsResolving Forces and EquilibriumResolving Forces-
OCR MEI A2 Maths 2017MechanicsResolving Forces and EquilibriumResolving Forces-
OCR-MEI A-Level (UK - Pre-2017)M1StaticsForces as vectors-
Pre-U A-Level (UK)MechStaticsForces as vectors-
Universal (all site questions)SStaticsForces as vectors-
WJEC A-Level (Wales)M1StaticsForces as vectors-