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1、Physics AS‐Unit 2‐Mechanics, Materials and Waves ‐Revision NotesMechanicsScalar and Vector Quantities•Definition –A Vector Quantity has magnitude as well as direction while a scalar quantity only had magnitude•Scalar –Distance, Speed, Mass•Vectors –Displ
2、acement, Velocity, AccelerationResultantabaa+bParallelogram Method22Pythagoras ‐a=b+cNote: when you know the resultant and drawing the horizontal and vertical component draw both of the components from the same point that the resultant starts from (resul
3、tant should be in‐between 2 components)Resolution Of Vectors•Resolves vector into horizontal and vertical components.aθyx•x=acosθ•y=asinθBalanced Forces•If an object is in equilibrium the two forces acting upon a point are equal and opposite to each othe
4、r and the sum of the anticlockwise moments = the sum of the clockwisemoments. No resultant force acting.•Equilibrium –3 forces –2 of the forces (resultant) are equal and opposite to the third force, there is no resultant force acting. Can also be drawn i
5、n a closed triangle.To calculate and unknown force or forces resolve each horizontally and vertically and solve, if object is in equilibrium there is no resultant force!Moments •Definition –The moment of a force about a point is equal to the force multip
6、lied by the perpendicular distance between the line of action (offorce) and the pivot (place taking moment about)•The principle of moments states that for an object to be in equilibrium the sum of the anticlockwise moments must equal the sum of the clock
7、wise moments at any point.Two Support Problems•If center of mass of beam is midway between both supports the force each support exerts is equal.•If not: oTake moments about S1 to calculate S2to work out S1or vice versaCouples•Definition –A couple is pair
8、 of equal and opposite parallel forces acting on a body but not at the same point.•The turning effect of a couple of equal and opposite forces is equal to One of the forces multiplied by the perpendicular distance between
