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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