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 moves is its speed. We can define speed as distance travelled by a body in unit time. 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. If we talk about acceleration, we come to know that the time rate of change of velocity is acceleration. Here, we will briefly explain speed, velocity and acceleration.

## What is speed?

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

= 200/20

Speed = 10 m/s

## What is the velocity?

The time rate of change of
displacement of a body is its 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, we can say that it is moving with uniform velocity.
Graph of uniform velocity gives us a straight line.

## Variable velocity

If a body covers unequal displacement
in equal intervals of time, it has 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 in East in 100
seconds, find out its velocity?

**Solution: **

Displacement = 300m

Time = 100 seconds

Velocity = Displacement / Time

= 300/100

Velocity = 3 m/s

## Difference between speed and velocity

After getting an idea about speed and velocity, we can compare these two quantities. Here, we will describe the difference between speed and velocity.

### 1. Difference between Meanings of Speed and Velocity

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. On the other hand, the meaning of velocity is the
displacement covered by a body in unit time.

### 2. Speed and Velocity Indicate Different Things

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 and Velocity are Two Different Quantities

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. Change of Direction

Speed of an object is always positive.
On the other hand, the velocity of an object can be positive or negative. It
means that we can’t change the direction of the speed of a body. On the other
hand, we can change the direction of the velocity of a body.

### 5. Magnitude

The magnitude of the velocity of a
body can be zero, positive or negative. On the other hand, the magnitude of the
speed of a body is always positive. In other words, the magnitude of the speed
of a body can never negative or zero.

### 6. The interrelation between Speed and Velocity

We can also inter-relate speed and
velocity. After inter-relating speed and velocity, we know that the speed of a
body may or may not be equal to its velocity. On the other hand, an object may
possess different velocities but its speed remains the same.

### 7. Units of Speed and Velocity

To measure both speed and velocity, we
use the same unit. We use ‘m/s’ to measure both speed and velocity of a body.

### 8. Equations

Speed and velocity have different
equations. To measure the velocity of a body, we use the equation ‘∆x/∆t’. This
equation gives us the average velocity of a body. On the other hand, to measure
the speed of a body, we use the equation d/t.

### 9. Calculations

We use two different techniques to
calculate the speed and velocity of a body. To calculate the velocity of a
body, we divide displacement over time. On the other hand, to calculate the
speed of a body, we divide distance over time.

### 10. Examples

Most of the students don’t know the
examples of speed and velocity. If we calculate the different speeds of a
sports bike, the average speed of the bike gives us the speed of the bike. On
the other hand, if a train moves in a particular direction, its average speed
will be its velocity.

Relevant Posts:

Difference
between Distance and Displacement

Difference
between Mass and Weight

## What is the Acceleration?

The time rate of change of velocity is
its 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. We use the following formula to
measure the acceleration.

**Acceleration = Velocity / Time**

## Uniform Acceleration

If the velocity of an object is the
same in equal intervals of time, it has 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, it has 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 its
SI unit. Its SI unit is m/s.

Velocity = 36km/h = 10 m/s

Time = 20 seconds

Acceleration = Change in velocity /
time

= 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 don’t understand the difference between velocity and acceleration. Here, we will discuss the key differences between velocity and acceleration.

### 1. Difference between Meanings of Velocity and Acceleration

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. Difference between Definitions of Velocity and Acceleration

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. Velocity and Acceleration Indicate Different Things

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. Velocity and Acceleration have Different Methods of Calculation

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. Units of Velocity and Acceleration

Unit of velocity is meter per second.
On the other hand, the unit of acceleration is meter per Second Square.

### 6. Formula

The formula of velocity is (d/t). On
the other hand, the formula of acceleration is (v/t).

### 7. Ascertains

With the help of velocity and
acceleration, we can make different ascertains. By calculating velocity, we can
get an idea of how fast an object is moving. Moreover, it also tells the
direction of the movement of the object. On the other hand, the acceleration of
an object tells how fast the velocity of an object is changing relevant to the time.

### 8. In Other Terms

If we multiple velocities of an object
with its mass, we will get its momentum
(p=mv). On the other hand, if we multiply the acceleration of an object with
its mass, we will get the applied force (f=ma).

### 9. Quantities

Both velocity and acceleration are vector
quantities. Its reason is that to measure these two quantities, we use
magnitude as well as direction.

### 10. Difference between Magnitudes of Velocity and Acceleration

As we have discussed earlier that the
magnitude of a velocity can be negative, positive or zero. On the other hand,
the magnitude of acceleration can also be positive or negative but it can never
be zero. Its reason is to find the acceleration of a body, there should be some
motion in the body.

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