Topics: Measurement, Observational error, Absolute deviation Pages: 8 (1464 words) Published: January 31, 2013
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Derived quantities

(speed is derived from dividing distance by time)
Derived unit
Combination of base units trough multiplying and/or dividing them

Example 1: Find the derived unit of Density

Unit Conversion
Area & Volume

Conversion of prefixes
Prefixes to normal number
Example 1
The frequency of the radio wave is 350M Hz. What is the frequency of the radio wave in Hz? Answer :
Mega (M) = 1,000,000 or 106
Therefore, 350MHz = 250 x 106Hz

Example 2
The thickness of a film is 25nm. What is the thickness in unit meter? Answer:
nano (n) = 0.000000001 or 10-9
Therefore, 25nm = 25 x 10-9 nm

Normal Number to prefixes

Example 3
0.255 s is equal to how many ms?
mili (m) = 0.001 or 10-3
To write a normal number with prefixes, we divide the number with the value of the prefixes 0.0255 s = 0.0255 ÷ 10-3 = 25.5 ms

Example 4
Convert 265,500,000 W into GW.
Giga (G) = 1,000,000,000 or 109
265,500,000 W = 265,500,000 ÷ 109 = 0.2655GW

Scientific notation

1.Scientific notation (also known as Standard index notation) is a convenient way to write very small or large numbers.

2.In this notation, numbers are separated into two parts, a real number with an absolute value between 1 and 10 and an order of magnitude value written as a power of 10.

3.Physical quantities that are very big or very small need to be written in the standard form so that it is neat, simple and easy to read.


1. 2,600 = 2.6 x 103
2. 75,300,000 = 7.53 x 107
3. 0.00023 = 2.3 x 10-4
4. 0.00000004121 = 4.121 x 10-6

Scalar and Vector Quantities
Scalar Quantity
1. Scalars are quantities which are fully described by a magnitude alone. 2. Magnitude is the numerical value of a quantity.
3. Examples of scalar quantities are distance, speed, mass, volume, temperature, density and energy.

Vector Quantity
1. Vectors are quantities which are fully described by both a magnitude and a direction. 2. Examples of vector quantities are displacement, velocity, acceleration, force, momentum, and magnetic field.

Example 1 
Categorize 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 Quantities:

* speed
* distance
* energy
* electrical charge
* density
* volume
* length
* time
* temperature
* mass
* power
* work

Vector Quantities:
* velocity
* acceleration
* displacement
* momentum
* force
* impulse

Measurements & error
Error is the difference between the actual value of a quantity and the value obtained in measurement.

There are 2 main types of error:

* Systematic Error
* Random Error

Systematic Error:
Systematic errors are errors which tend to shift all measurements in a systematic way so their mean value is displaced. Systematic errors can be compensated if the errors are known.

Examples of systematic errors:

1. zero error, which cause by an incorrect position of the zero point, 2. an incorrect calibration of the measuring instrument.
3. consistently improper use of equipment.

Systematic error can be reduced by:

1. Conducting the experiment with care.
2. Repeating the experiment by using different instruments.

Zero error

1. A zero error arises when the measuring instrument does not start from exactly zero. 2. Zero errors are consistently present in every reading of a measurement. 3. The zero error...
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