Physical Quantities and units Flashcards
What is a physical quantity?
Physical quantities are those which can be measured, for example: length, mass, weight, speed, force, momentum, time etc. Every physical quantities has a numerical value and a unit.
What are base quantities?
Base Quantities are those quantities which require only one measurement. They are seven in number.
How many base Quantities are there?
The seven base quantities are:
Length-meter-m
Mass-Kilogram-Kg
Time-Second-S
Electrical current-Ampere-A
Temperature-Kelvin-K
Amount of Substance-Mole-mol
Luminous Intensity-Candela-cd
What are base units?
The units of the base quantities are known as base units.
What are derived quantities?
Physical quantities other than base quantities are called derived quantities, as they require more than one measurement.
What are derived units?
They can be derived from the relationship between the derived quantities and the base quantities.
What are the derived Quantities?
Area
Volume
Density
Velocity
Acceleration
Force
Energy/work
Kinetic Energy
Potential Energy
Power
Pressure
Charge
Frequency
Momentum
Electrical resistance
Voltage
Strain
Spring Constant
Potential Difference
What is the formula and derived units for area?
LxL=pier^2
Derived units=mxm=m^2
What is the formula and derived units for volume?
LxLxL=m^3
Derived units=m^3
What is the formula and derived units for density?
mass/volume
Derived Units:
mass=kg
volume=m3
hence density=kg m-3
What is the formula and derived units for velocity?
velocity=distance/time
Derived Units:
distance: m
time: s
hence velocity= m s-1
What is the formula and derived units for acceleration?
acceleration: a = Δv/Δt
Derived Units:
Velocity: m s-1
time: s
hence acceleration= m s-2
What is the formula and derived units for force?
Force: mass x acceleration
Derived Units:
mass=kg
acceleration= m s-2
hence force= kg m s-2
What is the formula and derived units for energy/word?
Energy/work: force x distance
Derived units:
force: kg m s-2
distance: m
Hence energy/work: kg m^2 s-2
What is the formula for kinetic energy?
1/2 mv^2
where m=mass
v=velocity