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# Introduction To Physics

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### Introduction To Physics

1. 1. Base Quantities LESSON 1 The physical quantities which are used as the basis for the measurement and can’t be derived from other physical quantities. Understanding Physics There are five base quantities as shown in the following table: The study of the laws that determine the structure of the universe with reference to the matter and energy of which it consists. The study was divided into separated fields; heat , the Base Symbol Unit name Unit Measured quantity Abbreviation by properties of matter, light, sound ,wave, electricity, magnetism, mechanics, nuclear physics etc. Length In physics , there is the need to make careful observations, precise and accurate measurements. Mass Understanding natural phenomena and observing everyday objects such as a table, a mirror etc and Time discuss how they are related to physics concepts has always been a central aim of physics. Temperature The roots of all science are firmly based in experiment. Of course , mastering scientific skills Current applying scientific knowledge must be the important thing to learn physics. Derived Quantities The physical quantities which were derived from base Physical Quantities quantities by multiplication operation or division Physics is based on measurement. We discover operation or both physics by learning how to measure the quantities that are involved in physics and we call its as There are three examples for derived quantities as physical quantities. shown in the following table. Derived Symbol In term of Derived unit Unit The meaning of Physical Quantities quantity the base Abbreviation Physical quantities are quantities that can be quantities Area measured. Examples of physical quantities are length, mass, Velocity time, weight, pressure, current and force. Density A physical quantity is a property ascribed to phenomena, objects, or substances that be quantified. Example are: (i) Frequency of oscillation – frequency is the quantity and oscillation is the phenomenon (ii) Length of a wooden block – Length is the quantity and the wooden block is an object (iii) Density of water – density is the quantity and the water is the substance There are two types of the physical quantities, • Base quantities • Derived quantities 1
2. 2. Example 1 Solution State the following derived quantities in terms of the base quantities. (a) Acceleration (Hint: Acceleration = change of velocity ) time (b) Momentum (Hint : Momentum = mass x velocity ) Solution Example 2 State the base units for the following derived quantities: (a) Force Scalar and Vector quantities (Hint : Force = mass x acceleration ) A scalar is any quantity with size (magnitude) but without specified direction. (b) Impulse Examples of scalar quantities include mass, time, (Hint : Impulse = change of momentum) length, temperature, energy, work, speed and pressure. (c) Work (Hint : Work = force x displacement) A vector is any quantity with size (magnitude) and specified direction. Examples of vector quantities are displacement, weight, force, velocity, acceleration and momentum. 2
3. 3. TUTORIAL 1 1 Which one of the following is not a base 7 Which one of the following pairs of derived quantity? quantities is true? A B Length Weight A Work and mass C D Current Time B Force and current C Pressure and temperature 2 Which one of the following is not a base D Weight and potential difference unit? 8 Which of the following physical quantities is a A B Celsius Ampere base quantity C D Kilogram Second A The weight of an astronaut on the Moon’s 3 All derived quantities can be derived from base surface is 10 N. quantities by B The velocity of a cyclist rides a bicycle is 70 km h-1 A addition operation or subtraction C The perimeter of a field is 380 m operation D The power of a lamp is 60 W. B addition operation or subtraction operation or both 9 Which one of the base quantities is not involve C multiplication operation or division in acceleration? operation D multiplication operation or division A Length operation or both B Mass C Time 4 The S.I. base unit for mass is 10 Which one of the following apparatus is not A B gram miligram be used to measure the density of a metal C D kilogram mikrogram cube? 5 Which one of the base quantities is not involve A Ruler in force? B Stop watch C Triple beam balance A B Length Time C Temperature D Mass 11 Which one of the following derived quantities contains length and time only? 6 Which of the derived quantities is the combination of a base quantities only? A B Velocity Momentum B D Force Pressure A Force B Volume C Acceleration 3
4. 4. A B kg 2 m kg - 2 m C D kg m 2 kg m - 2 E kg 2 m 2 17 The period of oscillation for an inertial balance 12 is given by Which one of the following is true? T2= km Physical Type of S.I. Unit where quantity physical T = The period of oscillation and the unit is quantity s, A Momentum Derived Kg m s-2 m = Mass and the unit is kg quantity k = constant B Temperature Base quantity o C C Work Derived kg m 2 s -2 The units of k are quantity D Area m2 Base A B kg s2 kg- 1 s 2 quantity C kg s D kg- 2 s-1 13 The kinetic energy of a moving object is given E kg2 s by E=½mv2 18 Which of the following quantity is a scalar where m = mass and v = velocity. The number quantity. of the base quantities involve in the kinetic energy ,E is or are A B Weight Volume C D Force Acceleration A 1 B 2 19 Which of the following quantity is a vector C 3 quantity. 14 Which of the following pairs of physical A B Work Power quantities and S.I. units is true? C D Velocity Distance Physical S.I. unit 20 Which one of the following pairs of vector quantity quantities is true? A Area foot squared A Impulse and area B Weight Kilogram B Power and pressure C Power Joules per minute C Weight and velocity D Density Kilograms per metre cubed 21 (a) The current flows through a metal conductor is defined by the equation 15 Which one of the following is true? current = charge A The S.I. units of charge is A s time B The S.I. units of volume is cm 3 C The S.I. units of velocity is km j - 1 Based on the equation, which of the D The S.I. units of acceleration is cm s- 2 quantities above are 16 A physical quantity is given by M=¾ed2 (i) base quantities where the unit of e is unit kilogram and the unit of d is metre. The units of M are ....................................................... (ii) derived quantities 4
5. 5. ....................................................... …………………………………………. (b) The S.I. units of F, m ,M and R (b) What are the S.I.units of charge? ............................................................... The S.I. units of G (c) 22 The power of a student to run up a stair is given by the equation Power = force X displacement time (a) State the base quantities contain in the equation above. .................................................................... (b) State the power in term of base quantities. .................................................................... 20 The Newton’s law of universal gravitation state, the gravitational attraction force, F is directly proportional to the product of the mass ,m and M of two bodies and inversely proportional to the square of distance ,R between them. The law is given by the equation F=GmM R2 Based on the equation, (a) give one example of (i) the base quantities ………………………………………….. (ii) the derived quantities. ………………………………………….. (iii) the vector quantities 5