SI Unit and Other Velocity Units
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.
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
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
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
Speed is a scalar quantity. It gives no idea about the direction. However, the speed of the object can be positive, zero, or negative.
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
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.
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.
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
Miles per hour (mph)
Kilometers per hour (kmph)
Knot
Foot per second or ft /s or fps
Feet per minute or ft/ m or fpm
Foot per hour
Meter per hour
Inch per second
Kilometers per second (kps)
Centimeters per hour (cmph)
Meter per minute
Millimeter per minute (mmpm)
Mile per minute
Millimeter per second (mps)
Centimeter per minute
Speed of light
Benz (Bz)
FAQs on Unit of Velocity
1. What are the differences between Velocity and Relative Velocity?
The differences between velocity and relative velocity are as follows:
Velocity is the speed at which an object moves in a direction, measured with respect to a frame of reference that is relative to different points.
Relative velocity is defined as the rate of change of relative position of one object with respect to another and is measured in a frame where the object is either at rest or moving with respect to the absolute frame.
2. Can Velocity be Positive or Negative? State with Example.
Since velocity is a vector quantity, i.e., it has a direction.
For example, when I’m driving towards my office, my velocity is positive and when I am driving towards home from office, the velocity is negative as when the direction of the moment is opposite, my velocity would be negative. However, negative velocity doesn’t exist practically, it’s all about the direction we consider.
Hence, negative velocity implies the velocity in the opposite direction than what would be positive.
3. What is the difference between Speed and Velocity?
The most important difference between speed and velocity is that speed is a scalar quantity, while velocity is a vector quantity. Speed is simply taken as the ratio of the distance travelled and the time taken to cover such distance, while velocity is the difference between starting and endpoint during a time period. Velocity is a quantity that describes the movement of an object in terms of its direction and speed, while speed is simply the rate of movement of an object.
4. What is instantaneous velocity?
The velocity of an object at a particular instance of a time when time is fixed is known as instantaneous velocity. The instantaneous velocity of the object is calculated irrespective of the starting or end position. To calculate the instantaneous velocity, a very small displacement of an object is taken in an extremely small interval of time, where the time interval or delta “t” is taken close to 0. This is the differential method to calculate velocity.
