What is speed -acceleration- velocity-uniform motion -relative velocity -average speed ? - letsdiskuss
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ankit shukla

merchant navy | Posted on | Science-Technology

What is speed -acceleration- velocity-uniform motion -relative velocity -average speed ?


Software engineer at HCL technologies | Posted on

Well, you can get this information from any NCERT textbook, along with their formulas and examples. Anyway, here you go with whatever you want to know:


Letsdiskuss (Courtesy: betanews.com)

Let’s start with the scientific formula.

Speed, which is denoted by v in Physics, is

v = S/t

Where S is the distance covered by an object and t is the time taken to cover that distance.

Therefore, the speed of an object is the distance covered by an object in the given amount of time.

The S.I. unit of speed is m/s (meter per second), as distance is measured in meter and time is measured in second.

So how much fast or slow a vehicle is moving is determined by the speed of the vehicle, i.e., the time taken by the vehicle to cover a given distance.

Average Speed

(Courtesy: pagalguy.com)  

Average speed of any object is the rate at which the journey of that object takes place. Since the speed of any object can’t be constant or uniform throughout the journey, we calculate the average of the speed of the object at various instants, instead of calculating the total distance traveled in total time.

Uniform Motion

uniform-motion-letsdiskuss (Courtesy: keydifferences.com) 

Uniform motion is a straight line motion, in which equal amount of distance is covered in equal amounts of time intervals. The graph obtained for a uniform motion is always a straight line.
For example, if the speed of a vehicle is 20 m/s, it means that the car covers a distance of 20 meters every second for the given amount of distance and time.


(Courtesy: calcworkshop.com)

By definition, velocity is also the distance covered by an object in the unit time, but with the directional component.

Since every motion is not straight line or uniform motion, direction of a moving body also needs to be taken into account. Therefore, velocity is a vector quantity because it deals with both magnitude and direction, unlike speed which is a scalar quantity and deals only with the magnitude.

So for a windy path, you will calculate velocity, and not speed since the velocity at every instant is different in this case, unlike in the case of a straight line path where the average of speeds at all the instants is equal to the average of total speed.

Velocity is also denoted by v with a sign of arrow over it to denote that it is a vector quantity (optional). One more difference in velocity and speed is that here, it’s not total distance divided by time, but total displacement (also denoted by S), which is also a vector quantity like velocity.

So, the formula here remains the same as above,

v = S/t

Where, v is velocity, S is displacement, and t is time taken for the displacement.

Relative Velocity

relative-velocity-letsdiskuss (Courtesy: youtube.com)

Have you ever noticed, while travelling through train, car, or bus, that the trees, buildings, and even the Sun appear as moving backwards? But what actually happens is that you move forward and the objects are stationary. Similarly, the passengers sitting beside you are actually in motion, just like you, but to you, they appear in motion.

Therefore, the relative velocity of an object is its velocity with respect of some other velocity. The co-passengers appear to be stationary to you because there is no relative velocity between you and them (all of you are moving with a same velocity –that of the vehicle), while the trees or the sun appears to be moving because there is a relative velocity between you and the objects outside your vehicle.


The relative velocity is the velocity of an object or observer B in the rest frame of another object or the observer A. The general formula of velocity is :

Velocity of B relative to A is = v⃗ b−v⃗ a (Source: toppr.com)


acceleration-letsdiskuss (Courtesy: sites.google.com)

Acceleration is also a vector quantity just like velocity. In fact, acceleration is nothing but the rate of change of velocity. Hence, a vehicle is said to be accelerating, if it’s changing its velocity. This makes acceleration, a phenomenon of non-uniform motion because velocity doesn’t change under the influence of uniform motion. Acceleration is a vector quantity, which can be both positive and negative.

The formula of acceleration a is

a = v/t

Where v is velocity and t is time.

The S.I. unit of acceleration is m/s-2 (meter per second square). 


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