What Is The Difference Between Speed And Velocity And Acceleration?



Speed, velocity and acceleration describe the motion of a body but there is a difference between speed, velocity and acceleration. The rate at which a body move is known as its speed. We can define speed as distance travelled by a body in unit time is known as its speed. On the other hand, the velocity of a body tells us how fast a body is moving in a particular direction. We can define velocity as the time rate of change of displacement of a body is known as velocity. If we talk about acceleration, we come to know that the time rate of change of velocity is known as acceleration. Here, we will briefly explain speed, velocity and acceleration. After reading this article, you will clearly understand the difference between speed, velocity and acceleration.

What is speed?

As we have discussed earlier that distance travelled by a body in unit time is known as its speed. It is a scalar quantity because it is completely described by its magnitude and we don’t require direction to describe it. If the speed of an object is higher, it means that it moving at a faster rate. If the speed of an object is lower, it means that it is moving at a slower speed. As an SI unit of distance is ‘m’ and SI unit of time is ‘s’, therefore, the SI unit of speed is ‘m/s’.

Formula to calculate the speed

We can easily calculate the speed of an object by using the following formula;
       r= d/t
Here, r is known as speed, d is known as distance travelled and t is known as the time taken to travel this distance.

Numerical relevant to speed

A cyclist covers a distance of 200 meters in 20 seconds, find out its speed.
Solution:
Distance travelled by the cyclist = 200 meters
Time taken to travel this distance = 20 seconds
Speed = Distance / Time
Speed = 200/20
Speed = 10 m/s

What is velocity?

The time rate of change of displacement is known as velocity. The velocity of a body tells us how fast a body is moving in a particular direction. Therefore, velocity is a vector quantity because there requires magnitude as well as direction for its complete description. SI unit of velocity is m/s.

Uniform velocity

If a body covers equal displacement in equal intervals of time, its velocity is known as uniform velocity. Graph of uniform velocity gives us a straight line.

Variable velocity

If a body covers unequal displacement in equal intervals of time, its velocity is known as variable velocity. Graph of variable velocity doesn’t give us a straight line.

Formula to calculate the velocity

We can calculate the velocity of an object by using the following formula;
Velocity = Displacement / Time

Numerical relevant to velocity

If a man walks 300 m East in 100 seconds, find out its velocity?
Solution:
Displacement = 300m  ,    Time  = 100 seconds
Velocity = Displacement / Time
Velocity = 300/100
Velocity = 3 m/s

Difference between speed and velocity

After getting an idea about speed and velocity, we are able to compare these two quantities. The main difference between speed and velocity is explained below;
    1)    The first difference between speed and velocity is in their meanings. The meaning of speed is the distance covered by a body in unit time, whereas, the meaning of velocity is the displacement covered by a body in unit time.
    2)    Speed of a body tells us how fast a body is moving. On the other hand, the velocity of a body tells us how fast and in which direction a body is moving.
    3)    Speed is a scalar quantity because we don’t require direction for its complete description. Velocity is a vector quantity because there requires magnitude as well as direction for its complete description.
    4)    Speed of an object is always positive. On the other hand, the velocity of an object can be positive as well as negative.

What is the acceleration?

The time rate of change of velocity is known as acceleration. Acceleration is a vector quantity because there requires magnitude as well as direction for its complete description. If the velocity of a body is increasing, its acceleration is positive. On the other hand, if the velocity of a body is decreasing, its acceleration is negative. Unit of acceleration is meter per Second Square. Formula to find out the acceleration of an object is given below;
Acceleration = Velocity / Time

Uniform acceleration

If the velocity of an object is the same in equal intervals of time, its acceleration is known as uniform acceleration. If we draw a graph between velocity and time, we get a straight line.

Variable acceleration

If the velocity of an object is changing in equal intervals of time, its acceleration is known as variable acceleration. If we draw a graph between velocity and time, we can’t get a straight line.

Numerical relevant to acceleration


If a car starts from zero and gains a velocity of 36km/h after 20 seconds, find out its acceleration.
Solution:
As we know that km/h is not the SI unit of velocity, therefore, before solving it, we have to convert it into an SI unit that is m/s.
Velocity = 36km/h = 10 m/s
Time = 20 seconds
Acceleration = Change in velocity / time
Acceleration = 10 – 0 / 20
Acceleration = 0.5 meter per second square

Difference between velocity and acceleration


While studying motion, we have to come across with velocity and acceleration. Most of the students are not able to understand the difference between velocity and acceleration. The key difference between velocity and acceleration is given below;
     1)    There is a difference between the meanings of velocity and acceleration. The velocity of an object is implied on the speed of an object. On the other hand, acceleration of an object is implied on the change in the velocity.  
     2)    There is also a difference between the definitions of velocity and acceleration. We define velocity as the rate of change in displacement. On the other hand, the acceleration of an object is defined as the time rate of change in velocity.
    3)    The velocity of an object tells us the speed and moving direction of an object. On the other hand, the acceleration of an object tells us how the velocity of an object is changing.
    4)    We can find the velocity of an object by dividing displacement over time. On the other hand, we can find acceleration by dividing velocity over time.
    5)    Unit of velocity is meter per second and unit of acceleration is meter per Second Square.




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