SI System Some Practical Units of Length
BASIC UNITS 1 light-year (ly) = 9.46 × 1015 m
Unit 1 AU or ua = 1.5 × 1011 m
Dimension Unit Symbol
Length meter m l 1 parsec = 3.084 x 1016 m ≈ 3.26 ly
Mass kilogram kg m 1 nautical mile = 1.85200 km
Time second s t 1 micrometer or micron = 1×10−6 m
Electric Current ampere A I
Temperature kelvin K T
1 angstrom (Å) = 10−10 m
Luminous candela cd J
Amount of mole mol N
angle radian m·m−1 rad
solid angle steradian m2·m−2 sr
Important Derived Units Some Practical Units of Mass
Derived 1 quintal = 102 kg
Definition SI Unit
quantity 1 metric ton = 103 kg
Area Length square m2 1 atomic mass unit (amu) or dalton = 1.66
Speed / Displacement per unit x 10-27 kg
Velocity time 1 pound = 0.453592 kg
Force Mass x Acceleration Kgms-2
1 Chandrasekhar limit = 1.44 mass of the
sun = 2.864 × 1030 kg
Motion is a change in position of an object Kinematics
with respect to time.
It is a branch of mechanics, which deals with
It is typically described in terms of the motion of object.
displacement, direction, velocity,
acceleration, and time.
It is the length of actual path followed by
Scalar quantity an object in a particular time interval
during a motion.
It is a physical quantity which has only It is a scalar quantity and its unit is meter.
magnitude. e.g., mass, length, time, work, etc.
Its dimensional formula is [M0L1T0].
Vector quantity Displacement ( S )
It is a physical quantity which has magnitude It is a vector that is the shortest distance
as well as direction. e.g., velocity, from the initial to the final position of an
displacement, acceleration, etc. object during a time interval.
It is a vector quantity and its unit is meter.