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Motion and Forces Heat and cooling Electricity. How many significant figures? 2.00 × 10 3 0.00045 0.1900.

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Presentation on theme: "Motion and Forces Heat and cooling Electricity. How many significant figures? 2.00 × 10 3 0.00045 0.1900."— Presentation transcript:

1 Motion and Forces Heat and cooling Electricity

2 How many significant figures? 2.00 × 10 3 0.00045 0.1900

3 How many significant figures? 2.00 × 10 3 3 0.00045 2 0.1900 4

4 Scalar or vector? Force Speed Displacement Distance Mass Work Acceleration

5 Scalar or vector? ForceVector SpeedScalar DisplacementVector DistanceScalar MassScalar WorkScalar AccelerationVector

6 Use this convention Up = + Right = + Down = - Left = -

7 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

8 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 -

9 Motion You throw a ball vertically upwards. While its moving upwards, whats the sign of its; a) Acceleration b) Velocity c) Displacement

10 Motion You throw a ball vertically upwards. While its moving upwards, whats the sign of its; a) Acceleration - b) Velocity + c) Displacement +

11 Newtons Laws of Motion What is Newtons first law of motion?

12 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.

13 Newtons Laws of Motion What is Newtons second law of motion?

14 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.

15 Newtons Laws of Motion What is Newtons third law of motion?

16 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.

17 What are the equations? Force: Momentum: Kinetic energy: Gravitational Potential energy: Work: Power:

18 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

19 Force graph – what is the acceleration? Force (N) Mass (kg)

20 Force graph – what is the acceleration? Force (N) Mass (kg) a = F/m therefore, a = gradient (+)

21 Heat, Temperature and Internal energy Define: 1. Heat 2. Temperature 3. Internal energy

22 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

23 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.

24 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.

25 Objects A (metal) and B (plastic) are two at the same temperature and have the same mass. AB

26 If 100J of internal energy is removed from each object (A and B), will they be at the same temperature?

27 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.

28 So which object will have the higher temperature?

29 Plastic B

30 How did this happen?

31 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.

32 Accommodating thermal expansion

33 Equations Equation for energy associated with temperature change of an object? Equation for energy associated with phase change?

34 Equations Equation for energy associated with temperature change of an object? Q = mcT Equation for energy associated with phase change? Q = mL

35 Equations From Q = mL, there are 2 different L values can that be used. 1. L f = Latent heat of fusion (solid-liquid) 2. L v = Latent heat of vapourisation (liquid-gas)

36 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

37 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

38 Why?

39 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

40 What is the direction of a) electron flow? and b) current? -

41 -

42 Series and parallel circuits 6V

43 Series circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6V

44 Series circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6/2 = 3V 6V

45 Series circuit For each bulb, R = 2 Ω 1.Total resistance? 6V

46 Series circuit For each bulb, R = 2 Ω 1.Total resistance? R(total) = R + R = 2 + 2 = 4 Ω 6V

47 Parallel circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6V

48 Parallel circuit For each bulb, R = 2 Ω 1.Voltage through each globe? 6V 6V

49 Parallel circuit For each bulb, R = 2 Ω 1.Total resistance? 6V

50 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

51 Which device is ohmic?

52

53 Rest of lesson… Revise through WACE book OR Revise through STAWA book


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