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Motion and Forces Heat and cooling Electricity
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How many significant figures? 2.00 × 10 3 0.00045 0.1900
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How many significant figures? 2.00 × 10 3 3 0.00045 2 0.1900 4
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Scalar or vector? Force Speed Displacement Distance Mass Work Acceleration
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Scalar or vector? ForceVector SpeedScalar DisplacementVector DistanceScalar MassScalar WorkScalar AccelerationVector
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Use this convention Up = + Right = + Down =  Left = 
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Motion You stand on top of a cliff and drop a ball. What is the sign of the balls; a) Acceleration b) Velocity c) Displacement
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Motion You stand on top of a cliff and drop a ball. What is the sign of the balls; a) Acceleration  b) Velocity  c) Displacement 
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Motion You throw a ball vertically upwards. While its moving upwards, whats the sign of its; a) Acceleration b) Velocity c) Displacement
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Motion You throw a ball vertically upwards. While its moving upwards, whats the sign of its; a) Acceleration  b) Velocity + c) Displacement +
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Newtons Laws of Motion What is Newtons first law of motion?
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Newtons Laws of Motion What is Newtons first law of motion? Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
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Newtons Laws of Motion What is Newtons second law of motion?
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Newtons Laws of Motion What is Newtons second law of motion? The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.
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Newtons Laws of Motion What is Newtons third law of motion?
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Newtons Laws of Motion What is Newtons third law of motion? For every action force there is an equal and opposite reaction force. Forces act in pairs.
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What are the equations? Force: Momentum: Kinetic energy: Gravitational Potential energy: Work: Power:
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What are the equations? Force: F = ma Momentum: p = mv Kinetic energy: KE = 0.5mv 2 Gravitational Potential energy: PE = mgh Work: W = Fs = E Power: P = E/t
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Force graph – what is the acceleration? Force (N) Mass (kg)
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Force graph – what is the acceleration? Force (N) Mass (kg) a = F/m therefore, a = gradient (+)
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Heat, Temperature and Internal energy Define: 1. Heat 2. Temperature 3. Internal energy
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Heat, Temperature and Internal energy Heat Defined as the transfer of energy across a boundary due to a temperature difference. It is incorrect to say an object contains heat energy, it is correct to say internal energy
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Heat, Temperature and Internal energy Temperature A measure of how hot or cold something is. Defined from the average kinetic energy of atoms and molecules.
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Heat, Temperature and Internal energy Internal energy Defined as the energy (kinetic and potential) associated with the random, disordered motion of atoms molecules. Also known as invisible energy.
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Objects A (metal) and B (plastic) are two at the same temperature and have the same mass. AB
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If 100J of internal energy is removed from each object (A and B), will they be at the same temperature?
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No, because they will have a different specific heat capacities. Metal has a lower specific heat value which makes it more sensitive to heat transfer.
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So which object will have the higher temperature?
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Plastic B
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How did this happen?
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Thermal expansion As the temperature of a liquid or solid increases, the molecules vibrate faster and occupy more space. This results in a volume increase known as thermal expansion, thus the rails bent.
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Accommodating thermal expansion
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Equations Equation for energy associated with temperature change of an object? Equation for energy associated with phase change?
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Equations Equation for energy associated with temperature change of an object? Q = mcT Equation for energy associated with phase change? Q = mL
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Equations From Q = mL, there are 2 different L values can that be used. 1. L f = Latent heat of fusion (solidliquid) 2. L v = Latent heat of vapourisation (liquidgas)
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Heat transfer For each case, how does heat get transferred? 1. Table to hand 2. Saucepan to egg in boiling water 3. Sun to Earth
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Heat transfer For each case, how does heat get transferred? 1. Table to hand: Conduction, direct contact 2. Saucepan to egg in boiling water: Convection, convection currents circulating in water 3. Sun to Earth: Radiation, no medium in space
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Why?
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Static electricity Rub plastic comb with cloth Electrons transfer from cloth to comb Comb is negatively charged Comb brought near neutral paper and attracts positive charges in paper
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What is the direction of a) electron flow? and b) current? 
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Series and parallel circuits 6V
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Series circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6V
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Series circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6/2 = 3V 6V
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Series circuit For each bulb, R = 2 Ω 1.Total resistance? 6V
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Series circuit For each bulb, R = 2 Ω 1.Total resistance? R(total) = R + R = 2 + 2 = 4 Ω 6V
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Parallel circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6V
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Parallel circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6V 6V
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Parallel circuit For each bulb, R = 2 Ω 1.Total resistance? 6V
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Parallel circuit For each bulb, R = 2 Ω 1.Total resistance? 1 /R(total) = 1 /R + 1 /R = 0.5 + 0.5 = 1 R(total) = 1/1 R (total) = 1 Ω 6V
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Which device is ohmic?
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Rest of lesson… Revise through WACE book OR Revise through STAWA book
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