Chapter 1 measurements
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This document discusses the system of units used in physics. It defines fundamental and derived quantities, and explains that derived quantities are combinations of fundamental quantities. The seven base SI units are listed as the meter, kilogram, second, ampere, kelvin, mole, and candela. Prefixes are used to modify unit names to indicate multiplicative factors of powers of ten. The document also covers converting between different units, and how to determine the number of significant figures in calculations. Three examples at the end demonstrate applying concepts like unit conversions and significant figures to physics problems.
![a) Leading zeros
Zeros that precede all the non zeros digit
They do not count as significant figures
Ex: 0.000562 [3 s.f]
b) Captive zeros
Zeros between non zeros digits. They always count as
significant figures
Ex: 13.009 [5 s.f.]
c) Trailing zeros
Zeros at the end of numbers. They count as significant figures
only if the number contains a decimal point.
Ex: 200 [1 s.f.]
2.00 [3 s.f]
19
19
Rules for Significant Figures](https://image.slidesharecdn.com/chapter1measurements-130713122315-phpapp01/85/Chapter-1-measurements-19-320.jpg)
Chapter 1 measurements
- 1. System of Units Fundamental Quantities Derived Quantities Units Prefixes Conversion of Units Significant Figure
- 2. State the definition and differences of based and derived quantities. able to list down the SI Prefixes. know how to apply the significant figures make a conversion of any units given by using simple & common method of rational number method
- 3. SYSTEM OF UNITS Basic Quantities Derived Quantities Units Prefixes
- 4. Physical Quantities * Basis of physical quantities * Combination of one or more basic quantity quantities BASIC QUANTITIES DERIVED QUANTITIES •Basis of physical quantities •Example : Length (m) Mass (kg) Time (s) Temperature (K) Electric current (A) •Combination of one or more basic quantities. •Example : Area (m2) Volume (m3) Velocity (ms-1) Acceleration (ms-2)
- 5. Also known as Base Quantities 5 5 Fundamental Quantities Quantity Unit Abbreviation Length (l) meter m Time (t) second s Mass (m) kilogram kg Electric Current (I) ampere A Temperature (T) kelvin K Amount of Substance Mole mol Luminous Intensity candela cd Table 1: SI Base Quantity and Units
- 6. Other quantities which defined in term of seven (7) fundamental quantities. Example: Speed Work Force Electric Potential Power Frequency Angle 6 6 Derived Quantities
- 7. BASIC QUANTITIES COMBINATION OF QUANTITIES DERIVED QUANTITIES Length (Length)2 Area(m2) Length (Length)3 Volume(m3) Length, time Length/time Speed(ms-1) Length, time Length/(time)2 Acceleration(ms-2) Length, mass Mass/(length)3 Density(kgm-3) Mass, time (Mass x length)/(time)2 Force(kgms-2)
- 8. Physical quantities measured by using unit. Example: Length is a physical quantity. 1960 – General Conference on Weights and Measures decided on a universal system of unit called the International System or SI based on the metric system. UNITS Physical Quantity Unit of Measurements Symbol Length Metre m Mass Kilogram kg Time Second s Electric current Ampere A Thermodynamic temperature Kelvin K Amount of substance Mole mol Luminous intensity Candela cd
- 9. A way of writing numbers that accommodates values too large or small to be conveniently written in standard decimal notation. In scientific notation, numbers are written in the form: Example: An electron's mass is about 0.000 000 000 000 000 000 000 000 000 000 910 938 22 kg. In scientific notation, this is written 9.1093822 10−31 kg.
- 10. Used to simplify big numbers. Replace powers of ten. To make the calculation easier. Y, Z, E, h, da, a, z, and y are rarely used. PREFIXES
- 11. 2000 m = 2 x 103 m = 2 km 0.005 m = 5 x 10-3 m = 5 mm 45 000 000 bytes = 45 x 106 bytes = 45 Mbytes 0.00000008 s = 80 x 10-9 s = 80 ns 200 mA = 200 x 10-3 A PREFIXES Example :
- 12. Any quantity can be measured in several different units. Hence it is important to know how to convert from one unit to another. Multiplying or dividing an equation by a factor of 1 does not alter an equation. Example: Length: foot / inch / metre 12 12 CONVERSION OF UNITS
- 13. 3 km = ? m 1 km = 1000 m 3 km = 3 x 1000 m =3000 m OR 3 km = 3 km x 1000 m 1 km = 3000 m Conversion of Units
- 14. 45 cm = ? km km4.5x10cm45 km45x10cm45 m1000 1km cm100 1m xcm45cm45 4 5 CONVERSION OF UNITS
- 15. 35 km.hr-1 = ? m.s-1 11 ms9.72km.hr35 s m 60x60 35x1000 1hr km35 s60 1min min60 1hr km1 m1000 1hr km35 hr1 km35 CONVERSION OF UNITS
- 16. 20 kg.m-3 = ? g.cm-3 323 33 3 3 33 3 33 cm.g10x2m.kg20 cm g 100x100x100 1000x20 m1 kg20 cm100 m1 kg1 g1000 m1 kg20 m1 kg20 cm100 m1 kg1 g1000 m1 kg20 m1 kg20 CONVERSION OF UNITS
- 17. The digits that carry meaning contributing to its precision. Retain all figures during calculation. The leftmost non-zero digit is sometimes called the most significant digit or the most significant figure. The rightmost digit of a decimal number is the least significant digit or least significant figure. Numbers having three significant figures: 587 0.777 0.000999 121000 Numbers having two significant figures: 16 8.9 0.12 0.0082 17 17 Significant Figures
- 18. 1. Non zero integers always count as significant figures. 2. Zeros: There are three classes of zeros. • Leading zeros • Captive zeros • Trailing zeros 18 18 Rules for Significant Figures
- 19. a) Leading zeros Zeros that precede all the non zeros digit They do not count as significant figures Ex: 0.000562 [3 s.f] b) Captive zeros Zeros between non zeros digits. They always count as significant figures Ex: 13.009 [5 s.f.] c) Trailing zeros Zeros at the end of numbers. They count as significant figures only if the number contains a decimal point. Ex: 200 [1 s.f.] 2.00 [3 s.f] 19 19 Rules for Significant Figures
- 20. Multiplying or Dividing • Ex: 16.3 x 4.5 = 73.35 (but the final answer must have 2 s.f.) Therefore, 16.3 x 4.5 = 73 (2 s.f.) 20 20 Significant figure for final answer = the quantity which has the least number of significant figures Mathematical Operation For Significant Figures
- 21. Adding or Subtracting • Ex: 12.11 + 8.0 + 1.013 = 31.123 The final answer is 31.1 (1 decimal places) 21 21 Number of decimal places for final answer = the smallest number of decimal places of any quantity in the sum Mathematical Operation For Significant Figures
- 22. 1. Ohms law states that V = IR. If V = 3.75 V and I = 0.45 A, calculate R and express your answer to the correct number of significant figures. 2. If the resultant force on an object of mass 260 kg is 5.20 x 102 N, use equation F = ma to find acceleration. 3. If a car is traveling at a constant speed 72 km/h for a time 35.5 s, how far has the car traveled? (use distance = speed x time) 22 22 Exercise 1
- 23. 1. R = V/I = 3.75/0.45 = 8.3333333Ω Due to the least s.f. (0.45 = 2 s.f.), thus the answer is 8.3 Ω 2. Due to the least s.f. (260 = 2 s.f. ), thus the answer is 2.0ms-2 3. Change v=72km/h to m/s => 72km/3600s=20m/s 23 23 2 2 2 260 1020.5 / ms x mFa mssmtvl 7105.35/20 Due to the least s.f. (72x103m/h = 2 s.f.), thus the answer is 0.71 km or 7.1x102m. Solutions
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