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Types of forcesScalars and VectorsForces and its effectsNewtons LawsFrictions and its effectsFree body diagramsDynamics1

2What is a force?Push or pull that an object exerts on anotherProduces/Tend to produce motionStops/Tend to stop motionAlways act in a particular directionSI Unit: Newton (N)

Types of ForcesNature of force1. Contact forcePush experienced when 2 objects are pressed together2. WeightGravitational pull of Earth on object3. FrictionOpposes motion, exists between 2 surfaces in contact4. ResistanceOppose motion, viscous force found in fluids (air and water)5. Electric forcePush/pull between electric charges6. Magnetic forcePush/pull between magnets/magnetic materials

3Forces and MotionCauses stationary object to moveCauses moving object to increase/decrease speedCauses moving object to change direction of motionCauses moving object to stop

4QUESTIONS?5Newtons First LawBalanced forces, acceleration = 0Every object will continue in its state of rest or uniform motion in a straight line unless a resultant (unbalanced) force acts on it to change its state. Object at rests remains at restObject in motion remains in motion at constant velocity

6Newtons Second Law*Unbalanced forces, acceleration not 0Every a resultant force acts on an object of constant mass, the object will accelerate and move in the direction of the resultant force. The product of the mass and acceleration of the object is equal to the resultant force.Object at rest starts movingObject in motion changes velocity or direction or both

7Newtons Third LawFor every action, there is an equal and opposite reaction, and these forces act on mutually opposite bodiesIn pairs (action + reaction)

Equal in magnitudeAct in opposite directionsAct on different bodies8QUESTIONS?9

Friction and its EffectsAlways opposes motion between 2 surfaces in contactDue to irregularities on surfacesCauses object to slow to stopNegative effectsPositive effectsReduce cars efficiency by 20%Needed for grip and daily activitiesCauses wear and teat of moving parts in machinesUse in brakes to slow down carsUse wheelsInsert ball bearingsUse lubricants and polishing surfacesAir cushion10QUESTIONS?11Scalars and Vectors (RECAP)Scalar quantities: Physical quantities with ______ONLYEg: ???

Vector quantities: Physical quantities with ____ and ____Eg: ???

Resultant vector???? Single vector that produces the same effect as 2 or more vectors being added up12Addition of parallel vectorsSimple addition and subtractionIf same directions, ADDIf different directions, SUBTRACT the lesser amount from the greater amountDraw to scale if required (remember previous slide)ADDSUBTRACT13Addition of non - parallel vectors2 methods: Parallelogram method and tip-to-tail methodChoose appropriate scale

2. Draw given vectors with arrows pointing in the right direction with length representing magnitude according to scale

3. Complete the parallelogram

4. Resultant force is the diagonal arrowMeasure length for magnitudeMeasure angle for direction14Addition of non - parallel vectorsChoose appropriate scale

2. Draw given vectors with arrows pointing in the right direction with length representing magnitude according to scale

3. Draw vectors by connecting the tip of one, to the tail of the second

4. Connect the tail of the first to the tip of the second to find resultant forceMeasure length for magnitudeMeasure angle for direction15Free Body Diagrams

16QUESTIONS?17MassWeightGravitational field and Gravitational field strengthComparison between Mass and WeightInertiaDensityMass, Weight and Density18

19MassMeasure of amount of matter (atoms/molecules) in bodyCannot be changed by location, shape and accelerationSI Unit: Kilogram (kg)

WeightMeasure of FORCE resulting from gravitational pull exerted by EarthHas magnitude and direction (towards center of Earth)SI Unit: Newton (N)

20Gravitational fieldRegion surrounding Earth where mass experiences a force due to gravitational attraction Gravitational field strengthDefined as gravitational force acting per unit mass on an objectWeight depends on gravitational field strengthOn earth = 10N/kg21QUESTIONS?22

Comparison between Mass and WeightMassWeightAmount of matter in bodyDue to gravitational pull on bodyScalarVectorMeasured in kgMeasured in NConstant regardless of gravitational field strengthChanges according to gravitational field strengthMeasured by beam balance, calibrated electronic balanceMeasured by spring or compression balance

23InertiaReluctance of object to change its state of rest or motionDepends on mass, greater the mass, greater the inertia

DensityDefined as mass per unit volumeFixed property for pure substancesFloats if lower density than waterSink if higher density than waterSI Unit: kg/m3

24QUESTIONS?25