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  • 1. CHAPTER 4
  • 2. Work-What is Work?-How to Calculate Work?-How to Calculate work in a gas?
  • 3. ‘ Work is done when A forces moves to In Physics point at which it acts in the direction ofNO! Work is not going to the office… the forces. ‘Work Done = Force X Distance moved by force in the direction of the force (Joules) (Newton) (Metre)
  • 4. Examples 50 N 30 N 10M Work done= 50N-20N X 10 20NX10 200 Joules toward the right. 30 degree 10m So =40xcos30 X 10MTo count the work done in an object, (Force) (Direction)the force must be in the same direction in the direction they move.
  • 5. WORK DONE IN AN EXPANDING GAS Work Done By The Gas = Force X Distance Moved (Joule) Newton (N) Metre (m)Work Done On The Gas = Pressure X Change in Volume (Joule) Pascal (Pa) Metre cube (m^3)When the “gas expands”,work is done by gas. (Distance is moved)If the gas “Contracts” ,then work is done on the gas.(Volume increase or decrease)
  • 6. -What is Energy? -What is Potential Energy?The ability to do work. -What is Kinetic Energy?ENERGY
  • 7. What Is Energy?-Energy is the ability to do work.-Energy cannot be destroyed,nor created.-Energy can only change form.-Every move that we’re doing are consisted of Energy.-Energy have the SI of Joule.
  • 8. Potential Energy 3KG Potential energy is the ability of an object to do work as a result of its position or shape. 10m Potential Energy= Mass X Gravity X Height (Joule) Kilograms (Kg) 9.8 m/s^2 Metre (m)So:EP= 3 X 9.8 X 10EP= 294 Joules
  • 9. Kinetic Energy Kinetic Energy is the energy due to motion.30 KgVelocity= 10 m/s Kinetic Energy= ½ X Mass x Velocity^2 Joules Kg (m/s)^2 1/2MV^2 So: Ek= 1/2Mv^2 ½ X 20 X 10^2 1000 Joules
  • 10. Energy Conversion and Conservation
  • 11. Type Of Energy Energy cannot be created or destroyed. It can only be converted from one form to another. Energy ExplanationHere are a few example of the type of Potential Energy Energy Due to positionenergy that they can be converted into: Kinetic Energy Energy due to motion Elastic or Strain Energy due to stretching an object Energy Electrical Energy Energy associated with moving electric energy Sound Energy A mixture of potential and kinetic energy Wind Energy A particular type of kinetic energy Light Energy Energy released during chemical reaction Solar Energy Light energy from the sun
  • 12. EfficiencyWhat Is Efficiency ?Efficiency gives a measure of how muchof the total energy may be used and is not lost Energy Efficiency Formula? Efficiency = Useful Work Done/Total Energy Input X 100
  • 13. The Deformation Of Solid -Hooke’s Law -Strain Energy -Stress Energy -Young Modulus
  • 14. Hooke’s LawWhat is Hooke’s law?Hooke’s law states that, provided the elastic limit is not exceeded,the extension of a body is proportional to the applied load. Force =K.Extension (Newton) (Metre) Where K is constant . It is known as elastic constant or spring constant. Force is directly proportional to Extension
  • 15. Strain EnergyStrain Energy is energy storedin a body due to change of shape. Formula Straign Energy W = ½ K.Extension^2 Metre Joules
  • 16. The Young Modulus What is The Young Modulus? It is a constant of a particular material which enable us to find extensions knowing the constant and the dimension of a specimen. StressYoung Modulus = -------------------------------- Strain Stress = Force/Area Normal to the force Strain = Extension/Original Length If there is a tie,the area of the circle in the tie is the diameter. Because it is a normal to the force
  • 17. The behaviour of different material under tensile stress. Brittle Material Ductile MaterialA brittle material will snap when exceeding A ductile material will expand and fracturedthe ultimate tensile stress.EX:GlassFibre. when exceeding the ultimate tensile stress.EX:Metals
  • 18. The behaviour of different material under tensile stress.ENERGY
  • 19. Thermal/Heat Energy
  • 20. Specific Heat CapacityWhat is a specific heat capacity? It is the constant to produce an energy with a certain mass and changes in Temperature. Formula Q = Mass X C X Changes in temperature
  • 21. Thermal (Heat) Capacity What is a Thermal (heat) capacity? It is the quantity of the heat energy required to raise the temperature of the whole body by one degree.FormulaQ = C X Changes in temperature
  • 22. Specific Latent Heat What is a specific Latent Heat? It is the heat energy required to convert unit mass of solid to liquid without any change in temperature. FormulaQ = Mass X Latent heat of Fusion/VaporisationLatent heat of Fusion (Lf) = when Ice turns into water or water turns into IceLatent heat ofVaporisation(Lv) = when water turns into gas or gas turns into water.
  • 23. POWER
  • 24. What is Power? Power is the rate of doing work. Power have the SI of Watt/Second. Usually Your bills in the mail,consisted of KW/H instead of W/s .Formula Power= Work done/Time Taken Power=Force X Speed
  • 25. Moment Of Force
  • 26. Moment Of ForceWhat Is Moment Of Force? ThethaIt is the turning effect of a Force. ------------------------------------------ Moment Of Force = Force x distance Nm N m
  • 27. Couples What is a Couple? A couple consist of two forces , equal in magnitude F but opposite in direction whose lines of action do not coincide. r r Moment of Force = F x 2rF
  • 28. The Principle of Moments It is stated that ,for a body to be in rational equilibrium, the sum of the clockwise moments about any point must equal the sum of the anticlockwise moments about the same point. 30 m 10 m 20 m 0.1 N (10 x 0.1)=(20x0.1) + 30f 0.1 N FSum of the clockwise moments= (10 x 0.1) 1=2+30fSum of the anti clockwise = (20 x 0.1) + 30F Moments= 1-2 // -30 = - 29.
  • 29. Equilibrium: What the center of Gravity? The center of gravity of an object is the point at which the whole weight of the object may be considered to act.For a body to be equilibrium:-The sum of the forces in any direction must be zero.- The sum of the moments of the forces about any point must be zero.
  • 30. Thank You