Measurement of length and time

Usually when we are measuring, we would face errors such as parallex error, zero error and random errors.
Why is there parallex error? Our positioning of the eye is not parallel to the degree therefor we can't read the exact reading.
Why is there zero error? Usually this happens because of the equipments are old and spoilt. To avoid this, you gotta set it to the scale of 0 first, find the degree that is over shooting or below then after you had measured, minus and add in accordingly.
Why is there random errors? Because people are to anticipating that they estimated the wrong values. To avoid this, scientist usually measure it three times and then average it.

Equipment used for measuring length would be
Measuring tape-0 to 5m
Meter rule-0 to 1m
Vernier calipers-0 to 15cm
micrometer screw gauge-0 to 2.5cm

Vernier calipers: It can measure as exactly as 0.01cm
Micrometer screw gauge: It can measure as exactly as 0.01mm
stop watch: used to measure interval of time
Simple pendulum: Measure time for 20 oscillations
The period will be affected by the amplitude of oscillation and the mass of the bob.

Vector

Vector has both magnitude and direction. What is this direction I'm talking about? Now is the moment to clear your doubt. Take force as an example,


Student A uses 5N to push towards >> direction
Student B uses 6N to push towards >> direction
So the total force would be 11N towards >> direction.

It can also be in this case...
Student A uses 7N to push towards >> direction
Student B uses 4N to push towards << direction
This means that both forces are acting on each other. But student A exerts more force than student B so the force would be 3N acting towards >> direction. Easy isn't it?
The sum of two vector is known as resultant.
Vector can be calculated using a parallelogram method.
Sorry I have very limited source so I couldn't show it to you..

Scalar

Scalar only has magnitude. What is magnitude? Magnitude are the variable being measured. Example of scalar would be meter because it doesn't have a direction where the force is acting which means it has a fixed direction to where the force are acting. The magnitude can be added arithmatically.

Prefixes

Examples of prefixes would be..
Tera-10^12  T
Giga-10^9   G
Mega-10^6  M
Kilo-10^3   k
Deci-10^-1 d
Cent-10^-2 c
Milli10^-3 m
Micro10^-6 u
Nano10^-9 n
Pico10^-12 p

All calculation if included prefixes are to be in index notation

E.g  1.2 x 10^3   3 x 10^-3

SI unit

what are the basic SI units? the table below represents the SI units of it's base quantity, variable and SI unit.

Physical Quantity

What is physical quantity? A physical quantity is a quantity that can be measured. A physical quantity is made up of numerical magnitude and a unit. Note, all physical quantity must have a numerical magnitude for CALCULATION and a unit to represent the SI unit which I will touch on it later on.
The unit of a physical quantity is a standard magnitude of the physical quantity which is used to compare other magnitudes of the same physical quantity.
Example, the length of a room is 10m so it is 10 times the length of a metre rule.

Physical quantities, Units and Measurement

There are five parts in this chapter..

1. Physical Quantity
2. SI units
3.Prefixes
4.Scalars and Vectors
5.Measurement of length and time