# Physics Form One Magerezaacademy Sc Ke-Books Pdf

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Career opportunities in physics,1 Engineering civil. Electrical,Mechanical,Agricultural,Environmental,2 Meteorology. 3 Surveying,5 Astronomy, NOTE all science based careers i e doctors nurses technologists engineers. pharmacists etc need physics as a true foundation,Basic laboratory safety rules. 1 Proper dressing must be observed no loose clothing hair and closed shoes must be. 2 Identify the location of electricity switches fire fighting equipment first aid kit gas. and water supply systems, 3 Keep all windows open whenever working in the laboratory.
4 Follow all instructions carefully and never attempt anything in doubt. 5 No eating or drinking allowed in the laboratory, 6 Ensure that all electrical switches gas and water taps are turned off when not in use. 7 Keep floors and working surfaces dry Any spillage must be wiped off immediately. 8 All apparatus must be cleaned and returned in the correct location of storage after. 9 Hands must be washed before leaving the laboratory. 10 Any accidents must be reported to the teacher immediately. District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. CHAPTER TWO,MEASUREMENT I, In order to measure we need to know or define the quantity to be measured and the units. for measuring it In 1971 a system known as the International System of Units Systeme. Internationale and seven basic units were agreed upon as follows Other quantities can be. obtained from these basic quantities and are referred to as derived quantities. Basic quantity SI units Symbols,Length Metre m,Mass Kilogram kg. Time Second s,Electric current Ampere A,Thermodynamic temperature Kelvin K. Luminous intensity Candela Cd,Amount of substance Mole mol.
This is the measure of distance between two points in space The SI unit for length is the. metre m Therefore 1 km 1000 m,1 Hm 100 m,1 mm 0 001 m. Length is measured using a metre rule 100 cm tape measure 100 m 300 m 500 m. This is the measure of the extent of a surface It is a derived quantity of length Its SI units. are square metres m2 Other units are cm2 km2 etc Formulas are used to determine. areas of regular bodies while for irregular bodies an approximation of area is used. This is the amount of space occupied by matter The SI units for volume is cubic metre m3. Other sub multiples are cm3 mm3 and l Hence 1 m3 1 000 000 cm3 and 1l 1 000 cm3. Volume can be measured using a measuring cylinder eureka can pipette burette. volumetric flask beaker etc, This is the quantity of matter contained in a substance Matter is anything that occupies. space and has weight The SI unit for mass is the Kilogram kg Other sub multiples used are. grams g milligrams mg and tonnes t 1 kg 1 000 g 1 000 000 mg 100 tonnes A. beam balance is used to measure mass, This is mass per unit volume of a substance It is symbolized by rho and its SI units are. kg m3 Density mass volume, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. 1 A block of glass of mass 187 5 g is 5 0 cm long 2 0 cm thick and 7 5 cm high. Calculate the density of the glass in kgm 3, Density mass volume 187 5 1000 2 0 7 5 5 0 1 000 000 2 500 kgm 3.
2 The density of concentrated sulphuric acid is 1 8 g cm 3 Calculate the volume of 3 1. kg of the acid, Volume mass density 3 100 1 8 1 722 cm3 or 0 001722 m3. The following is a list of densities of some common substances. Substance Density g cm3 Density kg m3,Platinum 21 4 21 400. Gold 19 3 19 300,Lead 11 3 11 300,Silver 10 5 10 500. Copper 8 93 8 930,Iron 7 86 7 860,Aluminium 2 7 2 700. Glass 2 5 2 500,Ice 0 92 920,Mercury 13 6 13 600,Sea water 1 03 1 030.
Water 1 0 1 000,Kerosene 0 80 800,Alcohol 0 79 790. Carbon iv oxide 0 00197 1 97,Air 0 00131 1 31,Hydrogen 0 000089 0 089. The mass of an empty density bottle is 20 g Its mass when filled with water is 40 0 g and. 50 0 g when filled with liquid X Calculate the density of liquid X if the density of water is. 1 000 kgm 3,Mass of water 40 20 20 g 0 02 kg, Volume of water 0 02 1 000 0 00002 m3 Volume of liquid volume of bottle. Mass of liquid 50 20 30 g 0 03 kg, Therefore density of liquid 0 03 0 00002 1 500 kgm 3. Relative density, This is the density of a substance compared to the density of water.
It is symbolized by d and has no units since it s a ratio. Relative density d density of substance density of water. It is measured using a relative density bottle, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. The relative density of some type of wood is 0 8 Find the density of the wood in kg m 3. Density of substance d density of water,Density of substance 0 8 1 000 800 kgm 3. Densities of mixtures, We use the following formula to calculate densities of mixtures. Density of the mixture mass of the mixture volume of the mixture. 100 cm3 of fresh water of density 1 000 kgm 3 is mixed with 100 cm3 of sea water of density. 1030 kgm 3 Calculate the density of the mixture,Mass density volume. Mass of fresh water 1 000 0 0001 0 1 kg,Mass of sea water 1030 0 0001 0 103 kg.
Mass of mixture 0 1 0 103 0 203 kg,Volume of mixture 100 100 200 cm3 0 0002 m3. Therefore density mass volume 0 203 0 0002 1 015 kg m3. This is a measure of duration of an event The SI unit for time is the second s Sub. multiples of the second are milliseconds microseconds minute hour day week and year It. is measured using clocks stop watches wrist watches and digital watches. Accuracy and errors, Accuracy is the closeness of a measurement to the correct value of the quantity being. measured It is expressed as an error An error is therefore the deviation of measurement. to the correct value being measured The smaller the error the accurate the measurement. error sensitivity size measured 100, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. CHAPTER THREE, Force is a push or a pull Force is therefore that which changes a body s state of motion or. shape The SI unit for force is Newton N It is a vector quantity It is represented by the. following symbol,Types of forces, 1 Gravitational force this is the force of attraction between two bodies of given.
Earth s gravitational force is the force which pulls a body towards. its center This pull of gravity is called weight, 2 Force of friction this is a force which opposes the relative motion of two surfaces in. contact with each other Friction in fluids is known as viscosity. 3 Tension force this is the pull or compression of a string or spring at both its ends. 4 Upthrust force this is the upward force acting on an object immersed in a fluid. 5 Cohesive and adhesive forces cohesive is the force of attraction of molecules of the. same kind while adhesive is the force of attraction of molecules of different kinds. 6 Magnetic force this is a force which causes attraction or repulsion in a magnet. 7 Electrostatic force this is the force of attraction or repulsion of static charges. 8 Centripetal force this is a force which constrains a body to move in a circular orbit. 9 Surface tension this is the force which causes the surface of a liquid to behave like a. stretched skin This force is cohesive,Factors affecting surface tension. a Impurities they reduce the surface tension of a liquid i e addition of detergent. b Temperature rise in temperature reduces tension by weakening inter molecular. Mass and weight, Mass is the amount of matter contained in a substance while weight is the pull of gravity on. an object The SI unit for mass is the Kg while weight is the newton N Mass is constant. regardless of place while weight changes with place The relationship between mass and. weight is given by the following formula W mg where g gravitational force. Differences between mass and weight,Mass Weight, It is the quantity of matter in a body It is the pull of gravity on a body. It is measured in kilograms It is measured in newton s. It is the same everywhere It changes from place to place. It is measured using a beam balance Measured using a spring balance. Has magnitude only Has both magnitude and direction. District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. An astronaut weighs 900 N on earth On the moon he weighs 150 N Calculate the moons. gravitational strength Take g 10 N kg, Moons gravitational strength weight of astronaut on the moon mass of astronaut.
150 90 1 67 Nkg 1,Measuring force, We use a spring balance to measure force A spring balance is an instrument that uses the. extension of a spring to measure forces, The length of a spring is 16 0 cm its length becomes 20 0 cm when supporting a weight of. 5 0 N calculate the length of the spring when supporting a weight of. a 2 5 N b 6 0 N c 200 N, 5N causes an extension of 4 0 cm therefore 1 0 cm causes an extension of 4 5 0 8 cm. a 2 5 N 2 5 0 8 2 0 cm therefore length becomes 16 0 2 0 18 0 cm. b 6 0 N 6 0 0 8 4 8 cm therefore length becomes 16 0 4 8 20 8 cm. c 200 N 200 0 8 160 0 cm therefore length becomes 16 0 160 0 176 0 cm. Vector and scalar quantities, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. A scalar quantity is a quantity which has magnitude size only Examples are distance. mass speed, A vector quantity is a quantity which has both magnitude and direction Examples are.
displacement weight velocity,CHAPTER FOUR, Pressure is defined as the force acting normally perpendicularly per unit area The SI. units for pressure is newton per metre squared N m 2 One Nm 2 is known as one Pascal. Pressure normal force area or pressure thrust area Another unit for measuring. pressure is the bar 1 bar 105 N m2 1millibar 100 N m2. Calculating pressure, 1 A rectangular brick of weight 10 N measures 50 cm 30 cm 10 cm calculate the. values of the maximum and minimum pressures which the block exert when resting. on a horizontal table,Area of the smallest face 0 3 0 1 0 03 m2. Area of the largest face 0 5 0 3 0 15 m2,Maximum pressure 10 N 0 03 3 3 102 N m2. Minimum pressure 10 N 0 15 67 N m2, 2 A man of mass 84 kg stands upright on a floor If the area of contact of his shoes and.
the floor is 420 cm 2 determine the average pressure he exerts on the floor Take g. Pressure force area 840 0 042 20 000 Nm 2,Pressure in liquids. The following formula is used to determine pressure in liquids. Pressure h g where h height of the liquid density and g is force of gravity. 1 A diver is 10 m below the surface of water in a dam If the density of water is 1 000 kgm. determine the pressure due to the water on the diver Take g 10 Nkg 1. Pressure h g 10 1000 10 100 000 Nm 2, 2 The density of mercury is 13 600 kgm 3 Determine the liquid pressure at a point 76 cm. below the surface of mercury Take g 10 Nkg 1,Pressure h g 0 76 13 600 10 103 360 Nm 2. 3 The height of the mercury column in a barometer is found to be 67 0 cm at a certain. place What would be the height of a water barometer at the same place Densities of. mercury and water are 1 36 104 kg m3 and 1 0 103 kg m3 respectively. Let the pressure due to water be h1 1g1 h g hence, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. h1 h 1 6 7 10 1 1 36 104 911 2 cm or 9 11 m,U tube manometer.
It is a transparent tube bent into U shape When a liquid is poured into a u tube it settles at. equal level since pressure depends on height and they share the same bottom Consider the. following diagrams, For the levels to differ the pressure P 1 must be greater than P 2 hence. P 1 P 2 h g, If P 1 is the lung pressure P 0 is the atmospheric pressure then if the difference is h then. lung pressure can calculated as follows,P 1 P 0 h g. A man blows into one end of a U tube containing water until the levels differ by 40 0 cm if. the atmospheric pressure is 1 01 105 N m2 and the density of water is 1000 kg m 3. calculate his lung pressure, Lung pressure atmospheric Pressure liquid pressure. P1 P0 h g Hence P1 1 01 105 0 4 10 1000 1 05 105 N m2. Measuring pressure, 1 Simple mercury barometer it is constructed using a thick walled glass tube of length.
1 m and is closed at one end Mercury is added into the tube then inverted and. dipped into a dish containing more mercury The space above the mercury column is. called torricellian vacuum The height h if it is at sea level would be found to be. 760 mm Atmospheric pressure can be calculated as, P g h where mercury 1 36 104 kg m3 g 9 81 N kg h 0 76 m. Then P 1 36 104 9 81 0 76 1 014 105 Pa, NOTE this is the standard atmospheric pressure sometimes called one atmosphere. It is approximately one bar, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. 2 Fortin barometer this is a more accurate mercury barometer The adjusting screw is. adjusted first to touch the mercury level in the leather bag. 3 Aneroid barometer increase in pressure causes the box to contract the movements are. magnified by the system of levers and is transmitted to the pointer by the fine chain and this. causes the pointer to move The scale is suitably calibrated to read pressure Since pressure. falls or rises as altitude falls or rises the pointer can also be cal ibrated to read altitude. District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. 4 Bourdon gauge it is also called gauge pressure and is used in gas cylinders When air is. blown into the rubber tube the curved metal tube tries to straighten out and this causes. movement which is transmitted by levers and gears attached to a pointer This gauge can. measure both gas and liquid pressure, 1 The height of the mercury column in a barometer is found to be 67 0 cm at a certain place. What would be the height of a water barometer at the same place densities of mercury. 1 36 104 kg m3 and water 1 0 103 kg m3, Let the pressure due to water be h1 1 g1 and that of water be h g Then.
h1 1 g1 h g Hence h1 6 7 10 1 1 36 104 1 0 103 911 2 cm or 9 11 m. Application of pressure in gases and liquids, 1 Rubber sucker this is a shallow rubber cap Before use it is moistened to get a good. seal then pressed firmly on a smooth surface so that the air inside is pushed out The. atmospheric pressure will then hold it firmly, against the surface as shown below They are used by. printing machines to lift papers lifting glass panes. heavy metal sheets etc, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. 2 Drinking straw when a liquid is drawn using a straw air is sucked through the straw. to the lungs This leaves the space in the straw partially evacuated The atmospheric. pressure pushing down the liquid in the container becomes greater than the. pressure inside the straw and this forces the liquid into your mouth. 3 The syringe they work in the principle as the straw They are used by the doctors in. hospitals for giving injections, 4 Bicycle pump it uses two valves one in the pump greasy leather and the other in. the tire When the handle is pushed in the pressure inside the barrel becomes. greater than the one in the tire and this pushes air inside The valve in the tire is. made such that air is locked inside once pumped, 5 The siphon it is used to empty tanks which may not be easy to empty by pouring.
their contents out The tubing must be lowered below the base of the tank The. liquid flows out due to pressure difference caused by the difference in height h g. District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. 6 Lift pump,7 Force pump,Transmission of pressure in liquids and gases. It was first recognized by a French mathematician and physicist called Blaise Pascal in the. 17th century Pressure is equally distributed in a fluid and equally transmitted as shown in. the following, a Hydraulic brake system the master cylinder transmits pressure to the four slave. cylinders on each wheel The cylinders contain brake fluid Fluid is used because. liquids are almost incompressible When force is applied in the pedal the resulting. pressure in the master cylinder is transmitted to the slave cylinders This forces the. piston to open the brake shoes which then pushes the brake lining against the drum. This force the rotation of the wheel to slow down It is important to note that. pressure is equally distributed in all wheels so that the car doesn t pull or veer to one. District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. b Hydraulic press it consists of two pistons with different cross sectional areas Since. pressure is transmitted equally in fluids when force is applied in one piston it is. transmitted to the other piston The smaller piston is called the force while the. bigger piston is called the load They are used to lift heavy loads in industries. bending metals and sheets etc, 1 The area of the smaller piston of a hydraulic press is 0 01 m 2 and that of the bigger. piston is 0 5 m 2 If the force applied to the smaller piston is 2 N what force is. transmitted to the larger piston,Pressure force area hence P 2 0 01 200 Pa. District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke. Force Pressure Area 200 0 5 100 N, 2 The master cylinder piston in a car braking system has a diameter of 2 0 cm The.
effective area of the brake pads on each of the four wheels is 30 cm 2 The driver. exerts a force of 500 n on the brake pedal Calculate. a The pressure in the master cylinder,b The total braking force in the car. a Area of the master cylinder r2 3 14 cm2,Pressure force area 500 3 14 10 4 1 59 106 N m2. b Area of brake pads 30 4 cm2 Since pressure in the wheel cylinder is the. same as in the master cylinder,F Pressure Area 1 59 106 120 10 4 1 91 104 N. CHAPTER FIVE,PARTICULATE NATURE OF MATTER,States of matter. Matter is anything that occupies space Matter exists in three states solids liquids and. gases Matter can be changed in various ways which includes physical chemical and nuclear. a Physical changes they are normally reversible and no new substances formed. Examples are, i Change of state such as melting and vaporization.
ii Thermal expansion due to heating,iii Dissolving solids in liquids. iv Magnetizing,v Charging electrically, b Chemical changes they are irreversible and new substances are formed. Examples are,i Changes caused by burning, ii Changes occurring in some chemicals due to heating e g mercuric oxide. iii The reactions resulting from mixing chemicals to form other substances. c Nuclear changes these are changes occurring in nuclear substances which give off. some particles i e Uranium and Radium As this happens they change into other. substances, District mocks kcse past papers notes form 1 4 papers available on www kusoma co ke.

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