The unit of velocity can be defined as the ratio of unit of distance and unit of time. Students should not confuse velocity with speed as both are different from one another. Although the units of speed and velocity are similar, velocity, being a vector quantity, is defined as the rate at which an object changes its position with respect to a frame of time and reference.
The unit of velocity and speed is m/s, and the formula for average velocity is
[V=frac{s}{t}],
where
S- The total displacement
t – The total time taken
Velocity is a physical quantity that is used to measure the speed along with the direction of an object. Velocity is one of the most important attributes of a moving object and the foundation of mechanics in the subject of physics. The equations of motion and along with calculating the time taken by a body to cover a particular distance have immense use of the concept of velocity.
Speed:
Speed is a scalar quantity and is defined as the rate of change of position of an object in any position and time.
The formula for speed is
[S=frac{d}{t}] ,
where
s- The speed attained in m/s
d- The total distance travelled
t – The total time taken
Distance:
The length of the actual path traversed by the body during motion in a given interval of time is called the distance travelled by that body.
Distance is a scalar quantity and it can never be zero or negative during the motion of an object.
Displacement:
At a given interval of time, the displacement is defined as the shortest distance between the two positions of the body in a particular direction at that time and is given by the vector traced from the initial position to the final position.
Displacement is a vector quantity, i.e., it has both magnitude and direction. Therefore, in a given interval of time, it can be positive, zero, or negative.
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The SI unit of distance and displacement is meter, which is denoted by m. |
SI Unit of Velocity
The velocity of the body is defined as the rate of change of displacement of the body with time. It is also defined as the speed of an object in a given direction. The relation is given by
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Velocity = Displacement / Time. |
Velocity is a vector quantity, i.e., it has both magnitude (speed) and direction.
The velocity depends upon the displacement of the object, which means that velocity can be zero, positive, or negative, according to its displacement as zero, positive, or negative.
SI unit or MKS (Meter-kilogram-second) unit of velocity is also meter per second or m/s or m s⁻¹, where m/s is the SI base unit of velocity.
Velocity Unit Symbol
The symbol for the unit of velocity is ms⁻¹ or m/s.
SI unit of Average Velocity
The average velocity of the object is defined as the total displacement of the object divided by the total time taken. It is given by
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Average velocity = Total displacement/ Total time taken. |
The SI unit of average velocity is m s-1 or m/s.
The dimensional formula for the same is given by M L T-1
CGS (centimeter-gram-second) unit for velocity is cm s⁻¹ .
The SI Unit of Speed
Speed of an object is defined as the rate of change of position of an object in any direction. It is given by
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Speed = distance traveled/time taken. |
Speed is a scalar quantity. It gives no idea about the direction. However, the speed of the object can be positive, zero, or negative.
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The SI or MKS unit for the speed is m/s or ms⁻¹. The CGS (centimeter-gram-second) unit for the speed is centimeter per second or cm s⁻¹ or cm/s. |
Angular Velocity Units
The angular velocity of an object in a circular motion is specified as the rate of change of its angular displacement. It is usually represented by the symbol omega (ω), given by
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Angular displacement is a vector quantity. Its direction is the same as that of ΔӨ,
Where ΔӨ is the angular displacement and is defined as an angle made by an object moving around a circular path.
The SI unit of angular velocity is radians per second,
Where radian is a dimensionless quantity.
The SI unit of angular velocity is 1/ s or second⁻¹ or s⁻¹.
In S.I. base units: s⁻¹.
The dimensional formula for angular velocity:
M⁰L⁰T⁻¹
Angular Displacement Units
The angular displacement of the object moving around a circular path is defined as the angle made or traced by the radius vector at the axis of the circular path in a given time.
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Where angle (Ө) = arc / radius (r) |
Such as the motion of a stone when tied to a string makes an angle Ө, where Ө is the angle swept by the stone.
Angular displacement is a vector quantity.
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The unit of angular displacement is the radian |
Unit of Velocity of Light
The velocity of light is a fundamental constant that
corresponds to the speed of electromagnetic radiation in a vacuum and has a value approximately equal to 2.9979 x 10¹⁰ centimeters per second.
The unit of velocity of light is taken as the unit of velocity, i.e., SI or MKS unit is m/s and the CGS unit is cm/s.
Velocity Units
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Miles per hour (mph)
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Kilometers per hour (kmph)
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Knot
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Foot per second or ft /s or fps
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Feet per minute or ft/ m or fpm
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Foot per hour
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Meter per hour
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Inch per second
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Kilometers per second (kps)
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Centimeters per hour (cmph)
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Meter per minute
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Millimeter per minute (mmpm)
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Mile per minute
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Millimeter per second (mps)
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Centimeter per minute
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Speed of light
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Benz (Bz)