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# Chapter 4 Summary

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### Chapter 4 Summary

1. 1. CHAPTER 4
2. 2. Work-What is Work?-How to Calculate Work?-How to Calculate work in a gas?
3. 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. 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. 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. 6. -What is Energy? -What is Potential Energy?The ability to do work. -What is Kinetic Energy?ENERGY
7. 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. 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. 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. 10. Energy Conversion and Conservation
11. 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. 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. 13. The Deformation Of Solid -Hooke’s Law -Strain Energy -Stress Energy -Young Modulus
14. 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. 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. 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. 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. 18. The behaviour of different material under tensile stress.ENERGY
19. 19. Thermal/Heat Energy
20. 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. 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. 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. 23. POWER
24. 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. 25. Moment Of Force
26. 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. 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. 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. 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. 30. Thank You