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Physical Quantity

Physical quantity

~Quantity that can be measured and consists of numerical magnitude and a unit

Physical quantities can be either:

Based quantity

Derived quantity

Base Quantity

Definition A unit that is not combined with one other or more physical quantity

Base QuantityBase quantity

Symbol

SI unitSymbol for unit

Length l metre m

Mass mkilogra

mkg

Time t second sTemperature T Kelvin KElectric current

I ampere A

SI unit Systeme International

d’Unites (SI) Recommended by Eleventh

General Conference of Weight and Measure in 1960

Based on metric system Has 7 base unit

Derived Quantity

Definition Combination of two or more base quantities

All quantities except for based quantity

QUIZ 1

Volume of liquid is categorized in what quantity?

Based quantity

Derived quantity

QUIZ 2

Identify the based quantity(a) Force(b) Density(c) Electric current(d) Electric charge

Prefixes

Function:~to indicate fractions or multiples of SI units

Example 1A measurement is made and the result is as

shown below:

Power = 2000000 W

It can be rewritten in the form of standard form as shown below:

Power = 2.0 x 106 W = 2.0 MW

Mega = 106

Replace 106 with letter M

Example 2Change the value of  6.50 x10-

7 m in term of nano

 6.50 x10-7 m 1 x10-9 

= 650 μm

Nano = 10-9

have to divide it by 1 x10-9.

Scientific notation is a way of writing numbers that are too large or too small to be conveniently written in standard decimal notation. 

M x 10n

1 < M < 10 and n is an integer

How to Do it To figure out the power of 10,

think "how many places do I move the decimal point?"

If the number is 10 or greater, the decimal point has to move to the left, and the power of 10 will be positive.  

If the number is smaller than 1, the decimal point has to move to the right, so the power of 10 will be negative:

Example 3

0.0055 would be written as 5.5 × 10-3

Because 0.0055 = 5.5 × 0.001 = 5.5 x 10-

3

Scalar quantities Any physical quantity that has

magnitude but no direction Magnitude is the numerical

value of a quantity. Examples of scalar quantities

are distance, speed, mass, volume, temperature, density and energy.

Vector quantity Any physical quantity that

has magnitude and direction Examples of vector quantities

are displacement, velocity, acceleration, force, momentum, and magnetic field.

Example 4Categorize each quantity below

as being either a vector or a scalar.

Speed, velocity, acceleration, distance, displacement, energy, electrical charge, density, volume, length, momentum, time, temperature, force, mass, power, work, impulse.

Scalar quantity

Vector quantity

Speed DistanceEnergy DensityElectrical chargeVolume LengthTime MassTemperaturePowerWork

velocityaccelerationdisplacementmomentumforceimpulse

Addition vector  Two vectors can be added together to determine the result (or resultant)

Example 5

**Tips:

The direction will based on the large value of vector

Method of vector addition:

1. Tip-to-tail method2. Parallelogram method

Tip-to-tail method We can add any two vectors, A and B,

by placing the tail of B so that it meets the tip ofA. The sum, A + B, is the vector from the tail of A to the tip of B.

Note that you’ll get the same vector if you place the tip of B against the tail of A. In other words, A + B and B + A are equivalent.

A B

A + B

Parallelogram method To add A and B using the parallelogram

method, place the tail of B so that it meets the tail of A. Take these two vectors to be the first two adjacent sides of a parallelogram, and draw in the remaining two sides. The vector sum, A + B, extends from the tails of A and B across the diagonal to the opposite corner of the parallelogram. If the vectors are perpendicular and unequal in magnitude, the parallelogram will be a rectangle. If the vectors are perpendicular and equal in magnitude, the parallelogram will be a square.

The Pythagorean theorem

determining the result of adding two (and only two) vectors that make a right angle to each other

not applicable for adding more than two vectors or for adding vectors that are not at 90-degrees to each other.

HOMEWORKMultiple choice question

Subjective question