GCSE›AQA GCSE Physics›Mind mapsContact and Non-Contact ForcesAQA GCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsContact forcesAct only when objects are touchingFriction opposes motion between surfacesAir resistance is friction through airTension is the pull in a stretched ropeNormal contact force: surface support at right anglesNon-contactAct between separated objectsGravitational: attracts any objects with massElectrostatic: between charged objectsMagnetic: magnets or magnetic materialsRemember GEMWeightForce on an object due to gravityW=mgW = mgW=mgggg is field strength in N/kgActs at the centre of massMeasured with a newtonmeterTypes of forcecontact and non-contactNWgMass or weightMass (kg) is fixed everywhereWeight (N) depends on field strengthDirectly proportional to each other10 kg on Earth: 10×9.8=98 N10 \times 9.8 = 98\,\text{N}10×9.8=98NForce pairsEach object exerts a force on the otherApplies to contact and non-contactPush a wall: wall pushes backExam tipsWeight is non-contact, gravity acts at a distanceObjects weigh less on the Moon, same mass