QB003 – SCIENCE (BRIDGING)

QB003 – SCIENCE(BRIDGING) CHAPTER 1: UNITS AND MEASUREMENT

UNDERSTANDING OF UNITS & MEASUREMENT • State the base quantity, derived quantity and its unit • Express quantities using prefixes • Express quantities using scientific notation • Solve problems involving conversion of units • Measure physical quantities using appropriate equipments • Explain types of experimental errors

INTRODUCTION Physical quantities Base quantities Derived quantities Scalar quantities Vector quantities Measurement Prefixes Scientific notation (standard form Error Systematic error Random error CONCEPTUAL MAP

BASE QUANTITIES • Base Quantitiesare physical quantities that cannot be defined in term of other quantities. • Scientific measurement using SI units (International System Units). Table 1.1 Shows five base quantities and their respective SI units

DERIVED QUANTITIIES • Derived Quantities are physical quantities derived from combination of base quantities through multiplication or division or both Table 1.2 shows some of the derived quantities and their respective derived units

Scalar quantities are physical quantities that have magnitude only Vector quantities physical quantities that have magnitude and direction Scalar Quantities & Vector Quantities Table 1.3 shows a list of some examples of scalar and vector quantities

PREFIXES • Prefixesare used to simplify the description of physical quantities that are either very big or very small. Table 1.4 Lists some commonly used SI prefixes

STANDARD FORM Example 1.1 : • For each of the following, express the magnitude using a scientific notation. • The mean radius of the balloon = 100 mm • The mass of a butterfly = 0.0004 kg • Solution: • The mean radius of the balloon • = 100 mm • = 1.0 x 102 mm • The mass of a butterfly • = 0.0004 kg • = 4.0 x 10-4 kg Standard form or scientific notation is used to express magnitude in a simpler way. In scientific notation, a numerical magnitude can be written as : A x 10n, where 1 ≤ A < 10 and n is an integer

CONVERSION UNITS • Illustrates the usage of prefixes Example 1.2 : Convert 3.5 kilometer to meter. Solution 1km = 103m = 1000m therefore 3.5 km = 3.5 km x 1000m 1 km = 3.5  1000 m = 3500 m Example 1.3: Express 0.0005 Mg in g Solution 1kg = 103g = 1000g 1Mg = 106g = 1000 000g therefore 0.005 Mg = 0.0005 Mg x 1000 000g 1 Mg = 0.0005  1000 000 g = 500 g

CONVERSION UNITS Contoh 1.5: Convert 0.075 kW to mW. Solution kW → W → mW Therefore kW → W = 0.075 kW  1000 W 1 kW = 0.075  1000 W = 75 W W → mW = 75 W 1000 mW 1 W = 75 000 mW Example 1.4: Change 50 msec to sec. Solution 1 msec = 10-3 sec =0.001sec Therefore 50 msec = 50 msec x 1 sec 0.001 msec = 50 x 1 sec 0.001 = 50 x 10-3 sec = 50 x 10-2 sec = 0.05 sec

Example 1.6 : Change 60 km/j to m/s. Solution 1 km = 1000m 60 km/j = 60 km x 1000 m x 1 hr 1 hour = 60 minute 1 hr 1 km 3600 s 1 minute = 60 sec = 60 x 1000 m 3600 s = 16.67 m/s Example 1.7 : The density of pure water is 1000 kg m-3, what is its density in g cm-3 ? Solution 1 kg = 1000 g 1 m = 100 cm 1000 kg = 1000 kg x 1000 g x ( 1 m x 1 m x 1 m ) m3 m3 1 kg 100 cm 100 cm 100 cm = 1000 x 1000 g 1 00 00 00 cm3 = 1 g cm-3

EXERSICE Convert the following units • 120 cm in unit meter (m) • 550 mg in unit gram (g) • 5600 mV in KV • 9.81 m/s in unit km/j • 8500 cm2 in m2 • 908 g/cm3 in kg/m3 • 45 g/cm2 in kg/m2

MEASUREMENT INSTRUMENTS Micrometer screw gauge Vernier calipers Ruler

ERROR IN MEASUREMENT • An error is the difference between the measured value and the actual value. • There are 2 main types of errors in measurement • Systematic errors • May be due to the error in calibration of instruments • Zero error is due to non-zero reading when the actual reading should be zero • Random errors • Due to mistakes made by observer when taking measurement either through • incorrect positioning of the eye (parallax) or the instruments when taking • measurement • It may also occur when there is a sudden change of environmental factors • like temperature, air circulation and lighting

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QB003 – SCIENCE (BRIDGING)