for a body of given mass graph between velocity of the body and its linear Movement is
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Today’s topic Motion in a Straight Line is specially put together for all NCERT-based Class 11 Physics students. These notes will be helpful for having a quick revision of the chapter.
Topics covered in Motion in a Straight Line are:
Motion
Rest
Point Mass Object
Types of Motion
Speed
Various Types of Speeds
Different Graphs of Motion
Equations for Motion in a Straight Line
Motion
In our daily lives, we come across a lot of moving things. For example: a car passing through from one place to other, a person riding on a bicycle and many more instances like these. So, simply put, when an object changes its position with respect to its surroundings with time, then it is called in motion. If this motion is linear, it is treated as a case of motion in a straight line.
More examples: Football on ground, rocks falling from a cliff, motion of moon around earth, a person inside a moving bus with respect to person outside the bus, bird flying in sky.
Rest
But when an object does not change its position with respect to its surroundings with time, then it is called at rest. Remember that rest and motion are relative states. It implies that any object that is at rest in one frame of reference can also be in motion in another frame of reference at the same time.
Point Mass Object
We can conclude that an object is considered as a point mass object, when the distance travelled by it in motion is huge in comparison to its dimensions.
Types of Motion
One Dimensional Motion
The motion is called one dimensional motion when only one out of the three coordinates that specify the position of the object changes with respect to time. For example, the motion of a block in a train along a straight track, a man walking on a leveled or narrow road and object falling under gravity, etc.
Various Types of Speeds
Uniform Speed
It can be concluded that an object is travelling with uniform speed when it covers equal distances in equal intervals of time.
Variable Speed
An object is defined as travelling with variable speed when it covers equal distances in unequal intervals of time.
Average Speed
The total path length travelled needs to be divided by the total time interval during which the motion has taken place for defining the average speed.
Average speed = (Total path length)/(Total time interval)
It is a scalar quantity and its SI unit is ms‒1.
Let’s assume that a body covers distances S1, S2, S3… with speeds V1, V2, V3… respectively, in same direction then average speed is given by:
Vavg = {Total Distance Travelled}/{Total Time Taken} = {S1 + S2 + ….}/{(S1/ V1) + (S2/ V 2) +…}
Instantaneous Speed
The average velocity helps us know how fast an object has been moving over a given time interval. But it still does not tell us how fast it moves at different instants of time during that interval. For this, let’s define instantaneous.
v = Δx/Δt [where, Δt → 0]
⇒ v = dx/dt
Different Graphs of Motion
Distance Time Graphs
We can represent the change in the position of an object with time on the distance-time graph.
If you look at this graph, time is taken along the x-axis and distance is taken along the y-axis.
The Distance time graphs of a moving body is useful for calculating the speed of the body as they specially represent velocity.
Velocity time graphs
The variation in velocity with time for an object moving in a straight line can be represented by a velocity-time graph.
In this graph, time is given along the x-axis and the velocity is given along the y-axis.
The displacement of an object moving with uniform velocity can be given by the product of velocity and time. The area enclosed by velocity-time graph and the time axis will be equal to the magnitude of the displacement.
When a body is moving with a constant velocity, then the velocity time graph for this body is a straight line parallel to time axis as shown below in the figure 5.

The velocity time graph of uniformly changing velocity is shown in figure 6 and is a straight line. One can figure out the value of acceleration by using the velocity time graph.
When the velocity of a body changes keeps changing in a irregular manner, then the velocity time graph of the body is a curved line.
Equations for Motion in a Straight Line
There are three equations of kinematics.
1) vv = u+at+at
2) SS = ut+ 1/2at2
3) v2= u2+2as
Important note:
Where
v = Final velocity
u = Initial velocity
a = Acceleration
s = Distance traveled by a body
t = Time taken.
Hope you liked this article. Keep following me.
Topics covered in Motion in a Straight Line are:
Motion
Rest
Point Mass Object
Types of Motion
Speed
Various Types of Speeds
Different Graphs of Motion
Equations for Motion in a Straight Line
Motion
In our daily lives, we come across a lot of moving things. For example: a car passing through from one place to other, a person riding on a bicycle and many more instances like these. So, simply put, when an object changes its position with respect to its surroundings with time, then it is called in motion. If this motion is linear, it is treated as a case of motion in a straight line.
More examples: Football on ground, rocks falling from a cliff, motion of moon around earth, a person inside a moving bus with respect to person outside the bus, bird flying in sky.
Rest
But when an object does not change its position with respect to its surroundings with time, then it is called at rest. Remember that rest and motion are relative states. It implies that any object that is at rest in one frame of reference can also be in motion in another frame of reference at the same time.
Point Mass Object
We can conclude that an object is considered as a point mass object, when the distance travelled by it in motion is huge in comparison to its dimensions.
Types of Motion
One Dimensional Motion
The motion is called one dimensional motion when only one out of the three coordinates that specify the position of the object changes with respect to time. For example, the motion of a block in a train along a straight track, a man walking on a leveled or narrow road and object falling under gravity, etc.
Various Types of Speeds
Uniform Speed
It can be concluded that an object is travelling with uniform speed when it covers equal distances in equal intervals of time.
Variable Speed
An object is defined as travelling with variable speed when it covers equal distances in unequal intervals of time.
Average Speed
The total path length travelled needs to be divided by the total time interval during which the motion has taken place for defining the average speed.
Average speed = (Total path length)/(Total time interval)
It is a scalar quantity and its SI unit is ms‒1.
Let’s assume that a body covers distances S1, S2, S3… with speeds V1, V2, V3… respectively, in same direction then average speed is given by:
Vavg = {Total Distance Travelled}/{Total Time Taken} = {S1 + S2 + ….}/{(S1/ V1) + (S2/ V 2) +…}
Instantaneous Speed
The average velocity helps us know how fast an object has been moving over a given time interval. But it still does not tell us how fast it moves at different instants of time during that interval. For this, let’s define instantaneous.
v = Δx/Δt [where, Δt → 0]
⇒ v = dx/dt
Different Graphs of Motion
Distance Time Graphs
We can represent the change in the position of an object with time on the distance-time graph.
If you look at this graph, time is taken along the x-axis and distance is taken along the y-axis.
The Distance time graphs of a moving body is useful for calculating the speed of the body as they specially represent velocity.
Velocity time graphs
The variation in velocity with time for an object moving in a straight line can be represented by a velocity-time graph.
In this graph, time is given along the x-axis and the velocity is given along the y-axis.
The displacement of an object moving with uniform velocity can be given by the product of velocity and time. The area enclosed by velocity-time graph and the time axis will be equal to the magnitude of the displacement.
When a body is moving with a constant velocity, then the velocity time graph for this body is a straight line parallel to time axis as shown below in the figure 5.

The velocity time graph of uniformly changing velocity is shown in figure 6 and is a straight line. One can figure out the value of acceleration by using the velocity time graph.
When the velocity of a body changes keeps changing in a irregular manner, then the velocity time graph of the body is a curved line.
Equations for Motion in a Straight Line
There are three equations of kinematics.
1) vv = u+at+at
2) SS = ut+ 1/2at2
3) v2= u2+2as
Important note:
Where
v = Final velocity
u = Initial velocity
a = Acceleration
s = Distance traveled by a body
t = Time taken.
Hope you liked this article. Keep following me.
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