Grade 11 - physics Topic 1 SI Units.pptx

SI Units in physics

1. What is missing in the picture below? The length of the string ball is 50 For any measurement to make sense, it must include a number and a unit meter

2. Topic 1: SI Units Grade 11 Physics

3. List the common physical quantities and their units with abbreviations. Classify them into base and derived quantities. Explain the difference between the fundamental base units and the derived units. Write the derived units in terms of the fundamental base units (for velocity, acceleration, force, pressure, energy & power) Use prefixes to convert the SI base units ( giga to pico ) Validate physical equations using dimensional analysis of physical quantities. Lesson Objectives: ZH

4. Measurement Measurement → instruments → number + unit To compare quantities To know the measured quantity every number has a unit

5. Measurement Measurement → instruments → number + unit The length of the string ball is 50 meter For any measurement to make sense, it must include a number and a unit different units?! every number has a unit

6. SI Units Base Quantity Base Unit Symbol Length meter m Mass kilogram kg Time second s Electric current ampere A Temperature Kelvin K Amount of Substance mole mol Intensity of Light Candela cd Scientists around the world uses a unified system of units called the SI (International System of Units). In the SI there are seven base units for seven base quantities What about other quantities?! list SI units

7. 1 2 Quantity Basic Quantities Derived Quantities Combination of basic units It’s only the 7 quantities listed in the previous table Length has a unit of (m) Time has a unit of (s) It’s quantities come from more than one basic quantities Force: unit of (kg.m/s 2 ) Velocity: unit of (m/s) Single basic unit SI Units

8. SI Units The base quantities were originally defined in terms of direct measurements. Other units, called derived units , are created by combining the base units in various ways. Give examples: meter / second m/s velocity meter / second squared m/s 2 acceleration

9. SI Units A large number of derived units formed by combining base units according to the algebraic relations of the corresponding quantities (some of which are assigned special names and symbols and which themselves can be further combined to form even more derived units). Give examples: newton (N) kg·m / s 2 force pascal (Pa) N / m 2 pressure joule (J) N·m energy volt (V) kg⋅m 2 ⋅s −3 ⋅A −1 voltage watt (W) J / s power ohm ( Ω ) V / A resistance farad (F) C / V capacitance henry (H) V⋅s / A inductance hertz (Hz) 1 / s frequency

10. SI Units Which of the following is base quantity : speed meter light pressure mass second time electric current length Which of the following is base unit : meter kilometer meter/second cd tesla kilogram km kg What is the difference between base and derived quantities?? list SI basic quantities with units

11. List the common physical quantities and their units with abbreviations. Classify them into base and derived quantities. Explain the difference between the fundamental base units and the derived units. Write the derived units in terms of the fundamental base units (for velocity, acceleration, force, pressure, energy & power) Use prefixes to convert the SI base units ( giga to pico ) Validate physical equations using dimensional analysis of physical quantities. Lesson Objectives: ZH

12. Write the derived units in terms of the fundamental base units for the following: Velocity, where Acceleration, where   Practice question

13. Practice question Write the derived units in terms of the fundamental base units for the following: Force, where Pressure, where  

14. Practice question Energy, where or Power,  

15. List the common physical quantities and their units with abbreviations. Classify them into base and derived quantities. Explain the difference between the fundamental base units and the derived units. Write the derived units in terms of the fundamental base units (for velocity, acceleration, force, pressure, energy & power) Use prefixes to convert the SI base units ( giga to pico ) Validate physical equations using dimensional analysis of physical quantities. Lesson Objectives: ZH

16. Prefixes Prefix Symbol Multiplying factor Tera - T 10 12 = 1 000 000 000 000 Giga- G 10 9 = 1 000 000 000 Mega- M 10 6 = 1 000 000 Kilo- k 10 3 = 1 000 SI is an easy system because it is based on multiples of 10. Prefixes with units are used to convert to multiples and parts of the units. Each Prefix has its own symbol and multiplying factor. big e.g : kilometer ≡ kilo + meter … or 10 3 meter = 1000 m. identify the prefixes

17. Prefixes Prefix Symbol Multiplying factor Deci- d 10 -1 = 0.1 Ceti- c 10 -2 = 0.01 Milli- m 10 -3 = 0.001 Micro- μ 10 -6 = 0.000 001 Nano- n 10 -9 = 0.000 000 001 Pico- p 10 -12 = 0.000 000 000 001 Femto- f 10 -15 = 0.000 000 000 000 001 small Note : time has special multiples such as minute, hour and day, where: 1 minute = 60 seconds 1 hour = 60 minutes 1 hour = 3600 seconds 1 day = 24 hours identify the prefixes

18. Prefixes identify the prefixes 10 -15 10 -12 10 -9 10 -6 10 -3 1 10 3 10 6 10 9 10 12 f p n μ m k M G T 10 -2 10 -1 c d multiply powers: add them divide powers: subtract them reflex powers: converse sign 10 ‒ 6 × 10 ‒ 2 = 10 (‒ 6 + ‒2) = 10 ‒ 8 10 ‒ 6 ÷ 10 ‒ 2 = 10 (‒ 6 ‒ ‒2) = 10 ‒ 4   Powers!!?

19. Prefixes 25 cm = __________ m 1700 g = __________ kg 25 μ s = __________ s 500 mL = _________ L 1200 B = __________ MB 1) Prefix on the left (×) 2) Prefix on the right (÷) 25 ×10 -2 25 ×10 -6 500 ×10 -3 1700 1200 = 1700 ×10 ‒3 kg = 1200 ×10 ‒6 MB convert prefixes Two steps conversion: 10 3 10 6

20. Prefixes (two steps) Convert the followings: 1500 μ m = _________ cm 1500 μ m = _______________ cm 1500 ×10 -6 Convert 0.02 kg = ____ mg 1500 μ m = _____________ cm 1500 ×10 (-6 - -2) = 0.15 cm 1500 μ m = __________ cm 1500 ×10 -4 convert prefixes 10 -2

21. Prefixes (speed conversion) Note: 1 minute = 60 seconds 1 hour = 60 min = 60 × 60 s Convert the followings: 72 km/hr = _____ m/s two steps conversion 72 km = ________ m 72 ×10 3 72 ×10 3 m/hr = _______ m/s 72 ×10 3 20   convert prefixes 60 × 60

22. Prefixes (speed conversion) Note: 1 minute = 60 seconds 1 hour = 60 min = 60 × 60 s Convert the followings: 15 m/s = _____ km/hr two steps conversion 15 m = ________ km 15 ÷10 3 15 ÷10 3 km/s = ___________ km/hr 15 × 60 × 60 54 Powers!!?   convert prefixes 10 3

23. Prefixes (speed and time conversion)     notice units and conversion factors Time Conversion: 2 days = ______________ seconds 4 hours = __________ seconds 2 × 24 × 60 × 60 4 × 60 × 60 convert prefixes

24. Prefixes (examples) Convert the following prefixes: 2.5 mm = ________ m 25 s = _______ μ s 1 m/s = __________ km/hr 2.5 ×10 -3 25 ×10 6 1× (60 × 60) convert prefixes = 25 000 000 μ s = 0.0025 m 1000 = 3.6 km/hr 1 km/hr = __________ km/hr 72 × (1000) 60 × 60 = 20 km/hr 0.02 kg = ____________ mg 0.2 ×10 3 ÷ 10 –3 = 200 000 mg

25. Prefixes Use the right prefix for the following : using the right prefix Length (height) Mass Time (your age) Mm km m cm 0.000 8 0.8 800 800 000 g kg Mg 2000 2 0.002 weeks months years 1176 168 14

26. Prefixes List an appropriate SI base unit with a prefix for measuring the following: The mass of a ball __________ The length of soccer field __________ The diameter of large pizza __________ The distance from your home to school ______ Your mass __________ using the right prefix

27. List the common physical quantities and their units with abbreviations. Classify them into base and derived quantities. Explain the difference between the fundamental base units and the derived units. Write the derived units in terms of the fundamental base units (for velocity, acceleration, force, pressure, energy & power) Use prefixes to convert the SI base units ( giga to pico ) Validate physical equations using dimensional analysis of physical quantities. Lesson Objectives: ZH

28. We can check the validity of physics equations and formulae using dimensional analysis by following these steps: Rewrite the equation in terms of the units of the quantities given. If the right side matches the left side the equation is valid , otherwise it is not . Example 1: a student used the equation for acceleration to come up with a new one for final velocity in terms of acceleration, time and initial velocity. , Is it valid or not?, verify.   Validating equations and dimensional analysis

29. We can check the validity of physics equations and formulae using dimensional analysis by following these steps: Rewrite the equation in terms of the units of the quantities given. If the right side matches the left side the equation is valid , otherwise it is not . Example 2: a student used the velocity-time graph to derive equation for displacement in terms of acceleration, time and initial velocity. , Is it valid or not?, verify.   Validating equations and dimensional analysis

30. We can check the validity of physics equations and formulae using dimensional analysis by following these steps: Rewrite the equation in terms of the units of the quantities given. If the right side matches the left side the equation is valid , otherwise it is not . Example 3: , Is it valid or not?, verify.   Validating equations and dimensional analysis

31. Example: The force (F) is measured by the the SI unit ( kg.m /s 2 ) and given by F = m×a where (m) is the mass and (a) is the acceleration. Determine the SI unit of acceleration. Answer: F = m  a First, we make the acceleration the subject of equation: Divide both sides by m Reflexive property of equality m  a = F     Now we substitute units     Validating equations and dimensional analysis

32. Example : [ ] : unit of a, b, and c have units of meters, s = a , what is [s] ? a, b, and c have units of meters, s = a + b, what is [s] ? a, b, and c have units of meters, s = (2a + b)b , what is [s] ? a, b, and c have units of meters, s = (a + b) 3 /c , what is [s] ? a, b, and c have units of meters, s = (3a + 4b) 1/2 /9c 2 , what is [s] ? Validating equations and dimensional analysis

33. List the common physical quantities and their units with abbreviations. Classify them into base and derived quantities. Explain the difference between the fundamental base units and the derived units. Write the derived units in terms of the fundamental base units (for velocity, acceleration, force, pressure, energy & power) Use prefixes to convert the SI base units ( giga to pico ) Validate physical equations using dimensional analysis of physical quantities. Lesson Objectives: ZH The End