PHYSICS

“The branch of science which deals with the study of matter, energy & the interaction between them.”

PHYSICAL QUNATITIES:Those quantities which can be measured are called physical quantities.For example: Length, mass, time, acceleration, momentum etc.

NON-PHYSICAL QUANTITIES:Those quantities which cannot be measured are called non-physical quantities.For example: Like, Wish, Sorrow, Hate, Love etc.

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FUNDAMENTAL QUANTITYInternational system of units is based on seven independent quantities known as fundamental quantities. These are given below:

PHYSICAL QUANTITY

SYMBOL FOR QUANTITY

UNIT SYMBOL OF UNIT

Length l Meter mMass m Kilogram kgTime t Second s

Electric current I Ampere ATemperature T Kelvin K

Luminous Intensity Iʋ Candela cd

Amount of substance

n Mole mol

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DERIVED QUANTITYThe physical quantities other than fundamental quantities are all called derived quantities. For example:

PHYSICAL QUANTITY

SYMBOL FOR QUANTITY UNIT SYMBOL OF UNIT

Speed v Meter/second m/s

Acceleration a Meter/second2 m/s2

Volume V Meter3 m3

Force F Newton N

Pressure P Pascal P

Work W Joule J

Charge Q Coulomb C3

PREFIXESPrefixes are very useful in expressing some quantities which are either very small or very large.

For example: The distance between air molecules is 0.000 00001m, we can also mention this by using prefixes i.e. 0.01 μm.

One more convenient way to express large or small quantities is standard form i.e. in standard form, the distance between air molecules is 1x10-8 m.

NOTE: When point is drag on right hand then power in standard form is negative.When point is drag on left hand then power in standard form is positive. 10+

10-

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PRACTICE EXERCISE FOR STANDARD FORM❶12000 000 m

❷0.000 000 0003 m

❸1000 000 kg

❹0.000 000 1 s

❺6400000 m

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PREFIXESTerminology Symbol Value Numerical value

Pico p 10-12 0.000000000001

Nano n 10-9 0.000000001Micro μ 10-6 0.000001Milli m 10-3 0.001Centi c 10-2 0.01Deci d 10-1 0.1Zero - 0 0Deca D 101 10Hecto H 102 100Kilo K 103 1000

Mega M 106 1000000Giga G 109 1000000000Tera T 1012 1000000000000

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UNIT CONVERSIONSLength⎕m → km⎕cm → m⎕mm → m ----------------------------------------⎕km → x1000 m⎕⎕m → x100 cm⎕⎕m → x1000 mm⎕

Exercise:Convert the following:❶1000 cm to m❷200 mm to m❸50 km to m❹500 m to mm❺10 km to mm

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Mass⎕g → kg⎕mg → kg⎕mg → g ------------------------------------------⎕kg → x1000 g⎕⎕g → x1000 mg⎕

Exercise:Convert the following:❶1000 mg to kg❷50 kg to g❸2 kg to mg❹500 g to kg❺10 mg to g

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Time⎕s → minute⎕s → hour⎕s → ms

Exercise:Convert the following:❶1 day to s❷60 min to s❸2 min to ms❹5 s to ms

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SCALARS & VECTORSSCALAR QUANTITY:“Physical quantity which can only be specified by magnitude is called scalar quantity.”For example: Distance, Speed, Time, Length etc.

VECTOR QUANTITY:Physical quantity which can be specified by magnitude as well as direction is called vector quantity.”For example: Displacement, Velocity, Acceleration, etc.

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DRAWING A VECTORDraw a vector of a velocity of 20 m/s in the direction of N45°E.STEPS:• Choose an appropriate scale. In this case, we

may choose 1 cm to represents 5 m/s.

• The length of the arrow will represent the magnitude of the vector. To represent a velocity of 20 m/s using the above scale, the length of the arrow would be 4 cm.

• Using protractor, measure an angle N45°E. The arrow diagram is shown in figure.

Scale: 1 cm: 5 m/s

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ADDITION OF VECTOR(ALONG THE SAME STRAIGHT LINE)By addition of vector, we mean a single resultant vector.In figure A, two forces of magnitude 5 N & 3 N are acting towards right so their resultant will be 8 N

In figure B, two forces of 2 N & 4 N are acting on left & right respectively, their resultant is 2 N.

(A)

(B)12

HOME WORKQ: Three forces 3 N, 1.5 N & 6 N act on a mass as shown in figure. What is the resultant due to the three forces?

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METHODS OF ADDITION OF VECTORSWhen the vectors making an angle with each other rather then at the same straight line, then we use methods of vector addition.TIP TO TAIL RULE:• Consider two vectors & .• Join the head of vector with the tail of vector

without any change in magnitude & direction.• Then draw a resultant vector whose magnitude

is equal to the shortest distance between tail of vector to the head of vector .

• The direction of the resultant vector is directed from the tail of vector to the head of vector as shown in figure.

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PARALLELOGRAM METHODConsider two vectors 3 N & 5 N acting on a block as shown in figure. (Not in same straight line)To find the resultant force according to parallelogram, we use following steps:• Choose particular scale & draw forces using

arrows. Here arrow OA represents 5N & arrow OC represents 3N forces.

• Complete parallelogram OACB such that AC is parallel AB is parallel to OC & OA is parallel to BC.

• The resultant of the parallelogram can be drawn as a diagonal of the parallelogram OB directed towards point B. the length of the resultant is 7 cm which means resultant force is 7 N with direction of 18°. Scale: 1 cm: 1 N

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MEASURING INSTRUMENTS (LENGTH)

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LENGTH INSTRUMENT ACCURACY

Several meters Measuring tape 0.1 cm

Several cm to 1 m Meter rule 0.1 cm

Between 1 cm to 10 cm Vernier callipers 0.01 cm

Less than 2 cm Screw gauge 0.01 mm

METER RULE:The commonly used instrument to measure the length of objects such as wires or distance between two points. It is best to measure from 1 cm mark & then subtract 1 cm from final reading because of the wear & tear of zero mark.For accurate measurements, always place your eye vertically above the mark to avoid parallax error.

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VERNIER CALLIPERSThe commonly used instrument to measure the length of objects up to 0.01 cm small.Steps of reading vernier scale:• Read the division on main scale which is just behind or on the zero of

Vernier scale (In our case it is 18.2 cm)• Now see which division of Vernier scale coincides with the division of

main scale (In our case its 10)• Now multiply that coincident division with the precision of Vernier

callipers.CALCULATION:Main scale div. + Vernier div. x (Precision)18.2 + 10 x (0.01)18.2 + 0.118.3 cm

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SCREW GAUGEThe commonly used instrument to measure the length of objects up to 0.01 mm small.Steps of reading screw gauge scale:• Read the division on main scale which is just last visible on the datum

line. (In our case it is 12 mm)• Now see which division of Circular scale coincides with the datum line of

main scale (In our case its 40)• Now multiply that coincident division with the precision of screw gauge.CALCULATION:Main scale div. + circular div. x (Precision)12 + 40 x (0.01)12 + 0.412.4 mm

MEASURING INSTRUMENTS (TIME)

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Due to wide range of time intervals we want to measure, we need different types of measuring instruments.

We will be measuring time with:• Stop watch • Ticker tape timer

PERIODIC MOTIONSuch a motion which repeats itself after a particular interval of time is known as periodic motion. E.g: motion of pendulum, spring etc.Such repetitive motion is called OSCILLATION & the time required to complete one oscillation is called PERIOD.

PERIOD OF PENDULUM

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EXPERIMENT:Objective:To determine relationship between period & length of the pendulum.

Apparatus:• Thread• Bob• Meter rule• Cork• Stopwatch• Stand

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