# SS 1 Physics (1st Term) ## VISCOSITY

MEANING OF VISCOSITY Viscosity is the internal friction which exists between layers of the molecules of a fluid (liquid or gas) in motion. The viscosity of a fluid can also be defined as the measure of how resistive the fluid is to flow. It is a vector quantity & measured in pascal-seconds(pa.s). It can be defined mathematically as the ratio of the shearing stress to the velocity gradient in a fluid Viscosity (ŋ) =           Force Area x Velocity gradient  ……………………………………….1. Velocity gradient = velocity Length   …………………………………………………2   W = U +  V W – U- V = 0        ……………………………………………………………3. V = W – U (apparent or effective weight) where V-viscous force, W- weight, U- upthrust NB : Substances with low viscosity include water, kerosene, petrol, ethanol. Those with high viscosity are glue, syrup, grease, glycerine etc   Experiment to Determine the Terminal Velocity of a Steel Ball Falling Through a… Read More »VISCOSITY ## WORK, ENERGY AND POWER

WORK Work is said to be done whenever a force moves a body through a certain distance in the direction of force.  Work done can be defined mathematically as the product of the force and the displacement. It is a scalar quantity & measured in Joules W = F X d ……………………………………….1. W = mgh     ……………………………………….2. If a force is applied on a body at an angle Ø to the horizontal Work done to move the body on the horizontal plane = Fcos Ø x d ……………………………..3. Work done to raise the body to an appreciable height = Fcos Ø x d ………………………4. Examples- A boy of mass 50kg runs up a set of steps of total height 3.0m. Find the work done against gravity Solution m = 50kg, h = 3m, g = 10m/s2 Work done = mgh = 50 x 10 x 3 = 1500 Joules Energy Energy… Read More »WORK, ENERGY AND POWER ## PRESSURE, ARCHIMEDES’ PRINCIPLES, UPTHRUST & LAWS OF FLOATATION

PRESSURE Pressure is defined as the perpendicular force per unit area acting on a surface. It is a scalar quantity & measured in N/m2 or Pascal (pa).It can also be defined as the force per unit area, which is calculated by taking the total force and dividing it by the area over which the force acts. Force and pressure are related but different concepts. A very small pressure, if applied to a large area, can produce a large total force. P = F     ……………………………..1.    Where P-pressure, F- force (N) & A-area (m2­)        A NB: 1 bar = 105 N/m2 = 105 pa Example – A force of 40N acts on an area of 5m2. What is the pressure exerted on the surface? Solution F = 40N, A = 5m2, P = ? P =  F/A = 40/5 = 8pa   Pressure in Liquid Pressure in liquid has the following… Read More »PRESSURE, ARCHIMEDES’ PRINCIPLES, UPTHRUST & LAWS OF FLOATATION ## DENSITY & RELATIVE DENSITY

DEFINITION OF DENSITY The density of a substance is the mass per unit volume of the substance. Density = mass of a given substance Volume of the substance Density is scalar quantity& measured in kgm-3 (kilogram per cubic meter)   Determination of Density The determination of density involves the determination of a mass and a volume. The mass can be found by weighing. The density of a substance can be determined using a graduated density bottle.   Relative Density Relative density is also known as specific gravity. Relative density of a substance is defined as the density of the substance per density of water. R.D = Density of the substance Density of water R.D is also equal to the ratio weight of a substance to weight of an equal volume of water. As weight is proportional to mass R.D = mass of substance mass of equal volume of water  … Read More »DENSITY & RELATIVE DENSITY ## VECTOR & SCALAR QUANTITY, DISTANCE/DISPLACEMENT

VECTOR & SCALAR QUANTITY, DISTANCE/DISPLACEMENT, SPEED/VELOCITY, ACCELERATION, DISTANCE/DISPLACEMENT –TIME GRAPH, SPEED/VELOCITY–TIME GRAPH SCALAR & VECTOR QUANTITY A scalar quantity is defined as a quantity that has magnitude only but no direction. Typical examples of scalar quantities are time, distance, speed, temperature, volume, work, power, electric potential etc.  A scalar quantity or parameter has no directional component, only magnitude.  For example, the units for time (minutes, days, hours, etc.) represent an amount of time only and tell nothing of direction.  Additional examples of scalar quantities are density, mass, and energy.   A vector quantity is defined as a quantity that has both magnitude and direction. Typical examples of vector quantities are velocity, displacement, acceleration, force, momentum, moment, electric field intensity etc   POSITION Position is referred to as the point in which an object can be located or the place object is found. The position of an object on a plane… Read More »VECTOR & SCALAR QUANTITY, DISTANCE/DISPLACEMENT ## FRICTION

DEFINITION OF FRICTION Friction (Fr) is defined as a force which acts at the surface of separation between two objects or two bodies in contact and tend to oppose the motion of one over the other. It is simply force of opposition. We have two types of friction: (a) Static friction, Fs (b) Dynamic friction, Fd. Fs is greater than Fd   LAWS OF SOLID FRICTION Friction opposes the relative motion of two surfaces in contact. It is independent of the area of the surface of contact. It depends on the nature of the surface. It is proportional to normal reaction (R). It is independent of relative velocity between the surfaces   Fr α R Fr = μR………………….1. where Fr-frictional force   μ-coefficient of friction  &  R-normal reaction   The weight ( W) of an object is acting vertically downward.. the normal reaction (R ) is always acting perpendicular to the… Read More »FRICTION ## MOTION IN NATURE

FUNDAMENTALS OF MOTION Many scientists have studied motion and its properties because of its importance to life. The Italian, Galileo Galilei, who lived from 1564 to 1642, did the first systematic study of motion. The science of the study of motion done by Galileo is known as kinematics. Isaac Newton was another scientist who did detailed work on the study of motion.   Motion involves a change of position of a body with time. It also involves how things move and what makes them to move. Kinematics is the description of how objects move without regard to forces causing their motion, and dynamics deals with why objects move as they do.   TYPES OF MOTION There are four basic – types of motion. There are as follows. TRANSLATIONAL MOTION:- When a body moves from a point A, along the line AB to another point B (see Fig. 4.1), we say… Read More »MOTION IN NATURE ## MEASUREMENT OF MASS, WEIGHT, LENGTH & TIME

TECHNIQUES AND MEASUREMENT Measurement is an important aspect of physics or other sciences. No fact in science is accepted, no law is established, unless it can be exactly measured and quantified. As physics is based on exact measurements, every such measurement requires two things; first a number or quantity, secondly a unit, e.g. 20 metres as the length of a table tennis’s board.   MEASUREMENT OF LENGTH THE METRE RULE: The metre rule is often used to measure distances of a few centimetres to some metres, for example, the dimensions of a table or room. When longer distances are involved, tape rule can be used. 0.1 cm or 1mm is the smallest graduation on a metre rule.   CALLIPERS: Callipers are used to measure distances on solid objects where an ordinary metre rule cannot be applied directly. They are made of hinged steel jaws which are closed (in the case… Read More »MEASUREMENT OF MASS, WEIGHT, LENGTH & TIME ## INTRODUCTION TO PHYSICS

MEANING OF PHYSICS Physics is the scientific study of matter and energy and how they interact with each other. This energy can take the form of motion, light, electricity, radiation, gravity etc. Physics deals with matter on scales ranging from sub-atomic particles (i.e. the particles that make up the atom and the particles that make up those particles) to stars and even the entire galaxies. It can also be defined as a natural science that involves the study of matter and its motion through space-time, as well as all applicable concepts, such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.   Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Over the last two millennia, Physics had been considered synonymous with Philosophy, Chemistry, and certain branches of Mathematics and… Read More »INTRODUCTION TO PHYSICS

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