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Measurements

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1.general physics  1.1 length and time  -i-Physical Quantity Physical Quantities A physical quantity is a property of an object that can be measured with a measuring instrument. A physical quantity is usually expressed as “a magnitude ( numerical value)  and a  physical unit or more ” Example :- Normal body temperature of a healthy human being is  37  0 C -ii-Length Measuring Length. Length is “the distance between two points in a space”. According to SI units, the length quantity is expressed in meter. There are several kinds of measuring devices used to measure quantity of length, among others, are as follows. Tools used… a-   Measuring tape. b-   Ruler c-   Vernier callipers. d-    Micrometer Measurement of length Length is measured accurately through many methods. Here are some: Method Notes Ruler Used to make simple measurements accurate to  0.1 cm  (1 mm) Vernier caliper Used to make simple measurements accurate to
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Motion

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Speed Speed can be defined as the distance covered by a moving object in unit time taken. Speed is a  scalar quantity  and hence it can only be represented by magnitude not by direction.In other words, “ The speed of an object can also be considered as the magnitude of the velocity of the object ”.  Speed Formula : Speed =  D i s t a n c e   c o v e r e d T i m e   t a k e n   X =  d t   where,  X  = speed of the moving object;  d  = distance traveled by the moving object;  t  = time taken to travel distance ‘d’.  Formulas for finding area, gradient and acceleration are mentioned in image below. acceleration and deceleration are related to changing speed 
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Mass weight and density

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MASS AND WEIGHT AND DENSITY Weight  = force of gravity = mass x free fall acceleration = ma = mg Force = Weight = mg   the acceleration of free fall for a body near to the Earth is constant Notes:- 10 m/s 2  = 10 N/kg   Weight is the force which causes an object to accelerate downwards and has the value mg. The value of the acceleration caused by weight can be calculated from Newton’s second law, using the equation F = ma Weight unit is N (because it is a force) It is measured by spring balance   Mass     Weight Define It is the amount that body contains“It is not a force” It is the force of gravity acting on the body“It is a force” Units kg N  (kg.m/s 2 ) Scalar or vector Scalar quantity(No direction) Vector quantity(always vertical downwards) Device used to measure Pan  balance.Beam balance. Spring balance Dependence on place Mass of a body remains the same throughout the universe (doesn’t change from one place to another) Weight varies from one pl
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Effects of forces

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Effects of forces A force may produce a change in size and shape of a body bending, twisting, compression, extension are the main ways for a body to change size, shape and motion if two forces are acting on the same line they are either acting together or against each other. the resultant force of two forces acting together is the sum of the forces in the direction that they were pulling/pushing. if they are acting against each other the resultant force is the bigger force minus the smaller force in the direction of the bigger force. if the forces are the same size they cancel each other out. to calculate the force, mass or acceleration of an object you can rearrange the equation force = mass X acceleration (provided you have the other two variables). if you threw a tennis ball, how hard the throw was depends on it’s mass and how fast the throw was.
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Turning effects

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Moment
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Conditions of equilibrium

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Equilibrium  Centre of mass Scalers and vectors A scalar is a quantity that only has a magnitude (so it can only be positive) for example speed. A vector quantity has a direction as well as a magnitude, for example velocity, which can be negative. • More ways to add vectors (Pythagoras’s theorem and the parallelogram rule) : 
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Momentum

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momentum and impulse  A moving object has momentum. This is the tendency of the object to keep moving in the same direction. It is difficult to change the direction of movement of an object with a lot of momentum. You can calculate momentum using this equation: Momentum (kg m/s) = mass (kg) × velocity (m/s) Impulse  The units of impulse and momentum are equivalent [N s = kg m/s].  Ft = mv – mu                             Impulse Newton's second law (F net  = m • a) stated that the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object. When combined with the definition of acceleration (a = change in velocity / time), the following equalities result. F = m • a or F = m • ∆v / t   If both sides of the above equation are multiplied by the quantity t, a new equation results. F • t = m • ∆v This equation represents one of two primary principles to be used in the a
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