chapter 4 summary
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TRANSCRIPT
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Work
PowerEnergy
CHAPTER 4
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Work
-What is Work?-How to Calculate Work?-How to Calculate work in a gas?
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NO! Work is not going to the office…
In Physics
‘ Work is done whenA forces moves to point at which it acts in the direction of the forces. ‘
Work Done = Force X Distance moved by force in the direction of the force(Joules) (Newton) (Metre)
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Examples
10M
30 N50 N
Work done= 50N-20N X 10 20NX10 200 Joules toward the right.
30 degree
40N
To count the work done in an object,the force must be in the same direction in the direction they move.
So=40xcos30 X 10M
10m
(Force) (Direction)
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WORK DONE IN AN EXPANDING GAS
Work Done On The Gas = Pressure X Change in Volume
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)
Work Done By The Gas = Force X Distance Moved(Joule)
(Joule) Pascal (Pa) Metre cube (m^3)
Newton (N) Metre (m)
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ENERGYThe ability to do work.
-What is Energy?-What is Potential Energy?-What is Kinetic Energy?
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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.
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Potential Energy
10m
3KG
Potential energy is the ability of an object to do work as a result of its position or shape.
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
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Kinetic Energy
30 Kg
Velocity= 10 m/s
Kinetic Energy is the energy due to motion.
Kinetic Energy= ½ X Mass x Velocity^2 1/2MV^2
Joules Kg (m/s)^2
So:Ek= 1/2Mv^2 ½ X 20 X 10^2 1000 Joules
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Energy Conversion and Conservation
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Type Of EnergyEnergy cannot be created or destroyed.It can only be converted from one form to another.
Here are a few example of the type of energy that they can be converted into:
Energy Explanation
Potential Energy Energy Due to position
Kinetic Energy Energy due to motion
Elastic or Strain Energy
Energy due to stretching an object
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
Chemical Energy Energy released during chemical reactions
Nuclear Energy Energy associated with particle in the nuclei of atoms
Thermal Energy Sometimes called heat energy
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Efficiency
What Is Efficiency ?
Efficiency gives a measure of how much of the total energy may be used and is not lost
Energy Efficiency Formula?
Efficiency = Useful Work Done/Total Energy Input X 100
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The Deformation Of Solid
-Hooke’s Law-Strain Energy-Stress Energy-Young Modulus
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Hooke’s Law
What 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
Where K is constant . It is known as elastic constant or spring constant.
Force is directly proportional to Extension
(Newton) (Metre)
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Strain Energy
Strain Energy is energy stored in a body due to change of shape.
Straign Energy W = ½ K.Extension^2
Formula
Joules Metre
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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.
StrainYoung Modulus = --------------------------------
Stress
Strain = Extension/Original Length
Stress = Force/Area Normal to the force
If there is a tie,the area of the circle in the tie is the diameter.Because it is a normal to the force
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The behaviour of different material under tensile stress.
Brittle Material Ductile Material
A brittle material will snap when exceeding the ultimate tensile stress.EX:Glass Fibre.
A ductile material will expand and fractured when exceeding the ultimate tensile stress.EX:Metals
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The behaviour of different material under tensile stress.
ENERGY
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Thermal/Heat Energy
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Specific Heat Capacity
What is a specific heat capacity?It is the constant to produce an energy with a certain mass and changes in Temperature.
FormulaQ = Mass X C X Changes in temperature
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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.
Formula
Q = C X Changes in temperature
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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/Vaporisation
Latent heat of Fusion (Lf) = when Ice turns into water or water turns into Ice
Latent heat of Vaporisation (Lv) = when water turns into gas or gas turns into water.
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POWER
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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
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Moment Of Force
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Moment Of Force
What Is Moment Of Force?
It is the turning effect of a Force. ------------------------------------------
------------------------------------- F
Distance
Moment Of Force = Force x distance
Thetha
Nm N m
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Couples
F
F
What is a Couple?A couple consist of two forces , equal in magnitude but opposite in direction whose lines of action do not coincide.
Moment of Force = F x 2r
r
r
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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.
10 m
0.1 N
20 m
0.1 N F
30 m
Sum of the clockwise moments= (10 x 0.1)Sum of the anti clockwise = (20 x 0.1) + 30F
(10 x 0.1)=(20x0.1) + 30f1=2+30fMoments= 1-2 // -30 = - 29.
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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.
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Thank You