Physical quantities are fundamental in physics, serving as the basis for expressing the laws of nature. These quantities are divided into two categories: base quantities, which are independent and cannot be defined in terms of other quantities (such as length, mass, and time), and derived quantities, which are defined through combinations of base quantities (like velocity, acceleration, and force). Accurate measurement of these quantities is essential, and the International System of Units (SI) provides a standard for doing so. Derived units in SI are based on base units, and conventions for writing units, such as avoiding capital letters for unit names and using scientific notation, ensure consistency and clarity in scientific work.
What are physical quantities in physics?
Physical quantities are measurable properties used to describe physical phenomena, such as mass, length, time, and velocity. These quantities are fundamental for expressing the laws of physics.
What is the difference between base and derived quantities?
Base quantities are fundamental and cannot be defined in terms of other physical quantities, such as length, mass, and time. Derived quantities, like velocity and force, are defined by combinations of base quantities.
Can you give examples of base quantities?
Examples of base quantities include length (meter), mass (kilogram), time (second), electric current (ampere), temperature (kelvin), and amount of substance (mole).
What are derived quantities?
Derived quantities are physical quantities that are defined by combining base quantities. Examples include velocity (m/s), acceleration (m/s²), and force (newton, N).
What are SI units?
SI units (International System of Units) are the standard units used to measure physical quantities. These include base units like meter (m) for length and kilogram (kg) for mass, as well as derived units like newton (N) for force.
When converting units, which of the following is true?
a) Base units should always be written together without a space
b) A multiple of a base unit applies only to the base unit
c) Derived units are always larger than base units
d) Prefixes should be written after the unit
Answer: a) Base units should always be written together without a space
What is the standard unit of electric current in SI?
a) Volt
b) Ampere
c) Coulomb
d) Ohm
Answer: b) Ampere
Which of the following prefixes represents a factor of 103?
a) Milli-
b) Kilo-
c) Mega-
d) Giga-
Answer: b) Kilo-
Which of the following is true about the SI unit of temperature?
a) Its symbol is "K" and it is expressed in Kelvin
b) Its symbol is "°C" and it is expressed in Celsius
c) Its symbol is "C" and it is expressed in Centigrade
d) Its symbol is "F" and it is expressed in Fahrenheit
Answer: a) Its symbol is "K" and it is expressed in Kelvin
Which of the following is a correct example of writing a physical unit with a prefix?
a) 1km = 1000m
b) 1 millimeter = 1000mm
c) 1 kilometer = 1x102 m
d) 1 megawatt = 1000watt
Answer: a) 1km = 1000m