The International System of Units (SI), established in 1960, is a standardized system for measuring physical quantities that is used worldwide by the scientific community and most nations. It consists of three types of units: base units (representing fundamental quantities like length, mass, time, etc.), supplementary units (such as radians and steradians), and derived units (formed by combining base units). The SI system promotes simplicity and ease in calculations and follows specific conventions for unit names, symbols, and prefixes. Additionally, measurements are often expressed in scientific notation and must be converted to SI base units for calculations.
What is the International System of Units (SI)?
The International System of Units (SI) is a globally accepted system for measuring physical quantities, established in 1960 to provide consistency in measurements across the world.
Name the seven base units of the SI system.
The seven base units of the SI system are:
1- Length (meter, m)
2- Mass (kilogram, kg)
3- Time (second, s)
4- Temperature (kelvin, K)
5- Electric current (ampere, A)
6- Luminous intensity (candela, cd)
7- Amount of substance (mole, mol)
What are supplementary units in the SI system?
Supplementary units are units that are not classified as base or derived units, such as the plane angle (radian) and solid angle (steradian).
What is a radian?
A radian is the angle subtended at the center of a circle by an arc whose length is equal to the radius of the circle.
How are derived units formed in the SI system?
Derived units are formed by combining base and supplementary units. For example, velocity is derived from length and time, while force is derived from mass, length, and time.
What should be done before performing calculations with measurements in the SI system?
a) Measurements must be rounded off
b) All measurements should be converted to appropriate SI base units
c) Units can be mixed without conversion
d) Only the base units should be used
Answer: b) All measurements should be converted to appropriate SI base units
Which of the following is true about scientific notation in the SI system?
a) It uses powers of 2
b) The number must have two digits before the decimal point
c) It is used for expressing both large and small numbers
d) It should always have three digits after the decimal
Answer: c) It is used for expressing both large and small numbers
What is the unit of temperature in the SI system?
a) Celsius
b) Kelvin
c) Fahrenheit
d) Rankine
Answer: b) Kelvin
What is the base unit for mass in the SI system?
a) Pound
b) Gram
c) Kilogram
d) Ounce
Answer: c) Kilogram
Which of the following is the correct prefix for 10⁻³ in the SI system?
a) Mega
b) Kilo
c) Milli
d) Giga
Answer: c) Milli