Classroom Assistants Classroom Assistant Home How Science Works National Curriculum Pastoral Duties Pupil Misconceptions Risk Assessment Safety - General Teaching Resources Twitter to be informed about updates Whole School YouTube Vid-Clips Students Student Home How Science Works National Curriculum Pupil Misconceptions Risks during practical lessons Safety - General Twitter to be informed about updates YouTube Vid-Clips Student Teachers Student Teacher Home How Science Works National Curriculum Pastoral Duties Pupil Misconceptions Risk Assessment Safety - General Teaching Resources Twitter to be informed about updates Whole School YouTube Vid-Clips Teachers Teacher Home Crosswords General topics Interactive Spreadsheets PowerPoint Presentations Psychology and teaching and learning Revision Flashcards Student Teacher - Index Twitter to be informed about updates Wide Reading - Science in the news YouTube Vid-Clips UK Key Stages KS3 (Y7-Y9) KS4 (GCSE) KS5 ('A' Level) Practice Questions KS3 Questions GCSE Questions 'A' Level Questions Exam Skills Examinations Skills INDEX Accuracy and Precision Calculations - Setting them out English Langusge Sills in Science Equations Equipment - Correct Use Of Errors in a Practical Experiment Examiner Speak Graph Plotting Learning Styles Mathematical Skills Memory Skills Practical Investigations Results Tables Sankey Diagrams Scientist You Should Know About Significant Figures Units - help with learning them Units - Rules Units - S.I. Prefixes Units - Symbols
Topic Menu Atmosphere Earth's Atmosphere Atmospheric Pressure Pressure in the Oceans Atomic Accelerators Atom: Simple Structure Atomic nucleus Atomic Spectra Mass Difference Nuclear Binding Energy Particle Accelerators Photons Photoelectric Effect Radioactivity Rutherford's Model of the Atom Photoelectric Effect Wave-particle duality Electricity Electricity Menu Energy Acid Rain Electromagnetic Energy Future Energy Sources Global Warming Human Energy Intake Ozone Depletion Payback Time Power Stations Sankey Diagrams Sources of Energy Types of Energy Forces Center of Gravity (Mass) Circular Motion Density Dynamics Graphs: Velocity/Time and Displacement/Time Graphs Forces Floating and sinking Friction Gravity Hooke's Law Machines Mass Moments Momentum Newton's Laws of Motion Power Pressure Projectiles Stability Stopping Distances Terminal Velocity Vectors and Scalars Weight Work done by a force Young's Modulus Y11 - Discussion topics - Driving Geophysics Earth's Atmosphere Acid Rain Atmospheric Pressure Plate Techtonics Ozone Layer Depletion Pressure in the Oceans Richter Scale Seafloor Spreading Seismic Waves Structure of the Earth Tides Wegener Calorimetry Cavity Wall Insulation Conduction Convection Double Glazing Expansion Heat Latent Heat Experiment Specific Heat Capacity Pressure Cooker Cooking Radiation Temperature Scales - Dalek Problem Thermometers U-Values Light INDEX Camera Colour Diffraction Dispersion Drawing optical diagrams Electromagnetic Spectrum Eye Fibre Optics Interference L.A.S.E.R.s Lenses Mirror - concave Mirror - convex Mirror - plane Prisms - to divert light Prisms - to disperse light Polarization Refraction Reflection Shadows Straight path for light Total internal reflection Magnetism Magnetism - basics Electromagnetism Electromagnetism Experiment The Earth's magnetic field Levitation Electromagnetic Induction Transformers Magnetic Flux - Higher Level Motor Effect Motor Effect - Higher Level Matter Atom - simple structure Density Kinetic Theory of Gases - Higher level Boyle's Law Charles' Law Ideal Gas Mass Metals - structure and properties Particle Theory Semiconductors Wave Particle Duality Medical Physics Action Potential/option> CT Scanner Ear - Structure Ear - loudness perception Ear - dB and dBA scales Ear - acoustic attenuation L.A.S.E.R.s/option> MRI Nuclear Medicine Applications Particle Accelerator Appications - Cyclotron Optics: Eye and sight correction Optics: Lenses Optics: Ray diagrams Optical Fibres Particle Accelerator Appications - LINAC Ultrasound - basics Ultrasound - higher Level Video Link X-Rays Nuclear Atom: Simple Structure Atomic nucleus Atomic Spectra Mass Difference Nuclear Binding EnergyNuclear Power Particle Accelerators Photons Photoelectric Effect Radioactivity Rutherford's Model of the Atom Photoelectric Effect Wave-particle duality Particles Atom - simple structure Density Kinetic Theory of Gases - Higher level Boyle's Law Charles' Law Ideal Gas Mass Metals - structure and properties Particle PhysicsParticle Theory Semiconductors Wave Particle Duality Radioactivity Radioactivity INDEX - Basic Level Topics Radioactivity INDEX - Higher Level Radioactivity - Glossary of terms Radioactivity - discussion on nuclear fallout Ear - Structure Ear - loudness perception Ear - dB and dBA scales Ear - acoustic attenuation Sound Sound Ultrasound - basics Ultrasound - higher Level Space Big Bang Theory Black Holes Comets and Asteroids Constellations Cosmic Rays Earth: Day, Year & Seasons Eclipses Extraterrestrial Life Light Year Phases of the Moon Red Shift Satellites Solar System Stars Telescopes Universe GAME LINK - Launch a spaceship Temperature Cavity Wall Insulation Conduction Convection Double Glazing Expansion Heat Latent Heat Experiment Specific Heat Capacity Pressure Cooker Cooking Radiation Temperature Scales - Dalek Problem Thermometers U-Values Units Units - learning aids Units - rules Units - symbols Units - S.I. Prefixes Waves Analogue and Digital Coherence Damping of vibrations Diffraction Electromagnetic Waves Interference Oscilloscopes Polarisation Reflection Refraction Resonance SHM - Simple Harmonic Motion Sound Standing Waves Superposition Waves - basic
'Centre of gravity' or 'centre of mass'
The centre of mass of an object is the point through which the weight of that object acts in a uniform gravitational field - that is why it is often called the centre of gravity. The AQA syllabus says it is 'that point at which the mass of the body may be thought to be concentrated'. That is because we can draw the weight arrow (representing the weight of the whole object) from that point. However the weight isn't really concentrated there - there is just an even distribution of weight on either side of that point.
To stay upright we have to position our centre of gravity within our 'base' (our contact with the support we are standing on). Humans can get very good at balancing...
If you take moments about that point (along any plane) the sum of the moments will be zero - it will balance!
The centre of gravity is therefore the point at which you could balance the object. If you find that point you will be able to support it at that point and it will not topple over!
Look at the ice skater. She is being supported at her centre of gravity. When she moves her arms and legs or head she will shift that point slightly (by altering the moments of the weights on each side of that point). It takes a lot of practice and expertise to handle balancing a person!
These cardboard butterflies have little weights on the underside of their wings making the centre of gravity of the butterfly be just under the tip of its 'chin'.
They make a great demonstration of how moving the centre of gravity can be used to get an unexpected result... magic!
The centre of gravity point is always vertically below the point from which it is suspended from. Whatever orientation you suspend the object from this is always the case!
It is easy to find the centre of mass of a regular object. You just have to draw the lines of symmetry for it. Where they cross is the centre of mass. For a non-uniform object you have to carry out a little experiment to find the C of G.
Here is a mind boggling demo where the centre of gravity is outside the object...
... and here is the explanation of it!
Stability and Centre of Gravity
For an object to be stable its centre of gravity has to be below its point of suspension.
Click here to go to the page on stability