Priyanka jakhar

1. Motion in straight line
part 1
Priyanka jakhar

3. Mechanics :-- is the area of physics concerned with the motions of macroscopic objects. ... It can also
be defined as a branch of science which deals with the motion and forces on bodies not in the quantum realm.
Mechanics is that branch of Physics in which we study about state of rest or motion of the material object of
particle and their aquarium under the action of the external force
The four fundamental concepts of classical mechanics discussed so far, i.e., space, time, mass, and force, allow us
to introduce the so-called kinetic units.
Statics:-- which deals with forces acting on and in a body at rest.
An object may be at rest when several forces are acting on it but they are in equilibrium condition.
In static measurement of time is not necessary.
kinematics:--which describes the possible motions of a body or system of bodies.
Kinematics the study of motion of material objects of particles without considering the causes of
motion is called kinematics.
In kinematics measurement of time is necessary .
The word kinematics has been derived from the Greek word Kinema which means motion.
kinetics:--which attempts to explain or predict the motion that will occur in a given situation.
Dynamics the study of motion of the material objects or particles by considering the causes of
motion forces is called dynamics.
In dynamics measurement of time is necessary .
The word dynamic has been derived from the Greek word dynamics which means power.
Since motion is caused by force source dynamics is is based on the concept of force.

5. Rest:--Weuse the word‘rest’ veryoften. For example, whensomeoneis doing no work or lying on the bed, we
often say that the person is resting. Thismeans that the personis not moving. scientificallyas well, the word
‘rest’ has a similar meaning.
• Scientifically, we say an object is at rest whenthe position of the object does not change with time, with respect
to its surroundings.
Motion :--A body is said to be in motion if it changes its position with respect to its surroundings.
Basically, there are three types of Motion, Translatory motion, Rotatory motion, and Vibratory
motion. Some Other Examples of Motion are Linear motion, Random motion, Circular
motion, Uniform and Non-Uniform Motion.
Motion is change in position of an object with time.Motion of object along a
straight line is called rectilinear motion. Examples include flying kite, moving train,
earth’s rotation etc. Motion along a straight line
Motion along a straight line is described using only X-axis of the coordinate system.
Types of motion –
1) Rectilinear Motion- The motion in which a particle moves along a straight line is called
rectilinear motion. Example- Motion of a sliding body on an inclined plane.
2) Circular Motion- The motion in which a particle moves in a circular path is called circular
motion. Example- A string whirled in a circular loop.

6. Rectilinear motion Circular motion Oscillatory motion

7. 3) Oscillatory Motion- The motion in which a particle moves to and fro about a given point is
known as oscillatory motion. Example- Simple pendulum.
Types of Motion
In order to completely describe the motion of an object, we need to specify its position. For this, we need to
know the position co-ordinates. In some cases, three position co-ordinates are required, while in some cases
two or one position co-ordinate is required.
Based on these, motion can be classified as:
(i) One dimensional motion:- A particle moving along a straight-line or a path is said to undergo one
dimensional motion.
One dimensional motion the motion of an object is said to be One dimension if only one out of the three
coordinates which are required for specifying the position of the object changes with time.
For example, motion of a train along a straight line, freely falling body under gravity etc.
(ii) Two dimensional motion:-A particle moving in a plane is said to undergo two dimensional motion.
One dimensional motion the motion of an object is said to be One dimension if only two out of the three
coordinates which are required for specifying the position of the object changes with time .
For example, motion of a shell fired by a gun, carrom board coins etc.
(iii) Three dimensional motion:- A particle moving in space is said to undergo three dimensional motion.
One dimensional motion the motion of an object is said to be One dimension if all the three coordinates which
are required for specifying the position of the object changes with time.
For example, motion of a kite in sky, motion of aeroplane etc.

8. Point Object:-If the length covered by the objects are very large in comparison to the size of
the objects, the objects are considered point objects.
• Reference Systems:-The motion of a particle is always described with respect to a
reference system. A reference system is made by taking an arbitrary point as origin and imagining
a co-ordinate system to be attached to it. This co-ordinate system chosen for a given problem
constitutes the reference system for it. We generally choose a co-ordinate system attached to the
earth as the reference system for most of the problems.
Rest and motion are relative terms :-It means an object may be in a state of rest with
respect to one object but at the same time it will be at in state of motion with respect to
other object.
Absolute rest and motion are not known:- State of rest and motion of a body are said
to be absolute if a reference point is available which is fixed or at rest.Scince our earth is
revolving continuously around the sun so no such point is available on the earth. In a similar
manner the entire solar system rotates about the galastic centre and the cluster of galaxies
move with respect to other cluster.
Thus no object in the universe is in the state of absolute rest and has absolute motion also can
not be realised .Only relative term and the relative motion can be realise partially.

9. Note :- 1. We Can take any point as absolute according to our convenience.
2. Direction as well as distance both is required to know ones position.
Relative and Absolute Position
In the figure position of B with respect to A is ABEast
In Respect to C is CB North East.
Thus position of a particular point can vary with
different points
•This is known as Relative Position .
•But in order to consider all points in one frame we
need to consider one point as a absolute referral
point an position of all other points with respect to
that point will be their
Absolute Position.
For example consider 0 as a absolute point then
position of all other points with respect to 0 will be
their absolute position for B is OB in North East.
Similarly A is OA North West and So On.
south D
East
C

10. 1) Position - It is defined as the point where an object is situated. Position can be determined by the
coordinate axis that is, marked in units of length and that has positive and negative direction.
Example- If an object is situated at -1m then minus sign indicates that the position has negative direction but if
the object at 0m position then it will be said to be at rest.
2) Frame of Reference- The fixed point or place with respect to which the position velocity and acceleration
of a body is measured is known as frame of reference.
In order to know the change in position of an object, a reference point is required. Point O in the
figure is the reference point or Origin and together with three axes, this system is called
the coordinate system. A coordinate system with time frame is called frame of reference.
•Objects changing positions with time with respect to the frame of reference are in motion while
those which do not change position are at rest.
•For a moving car, for the frame of reference outside the car, it appears moving. While for the frame
of reference inside the car, the car appears stationary.
Frame of reference are of two types :-
1) Inertial frame of reference :- Any frame of reference which is either at rest or moving with uniform
velocity is called Inertial frame of reference.
Example :- A plane moving on a horizontal track with constant is an inertial frame reference.
2) Non-Inertial Frame of reference :- A frame of reference which is accelerated is called non-inertial frame
of reference.
Example :- Body falling down under the force of gravity.

12. 3) Path length and Distance :- The path covered by a object in a given time interval, is called Path length or
Distance.
It is the distance between two points along a straight line. It is scalar quantity.
Example :- Suppose an object moves along xaxis to a distance of 100m from the origin in time
‘t’. Then the path length is 100m.
4) Displacement :- The shortest distance from the initial position to the final position of the
particle is called displacement. Displacement = x2 – x1
It is the change in position in a particular time interval. It is vector quantity. Change is position is
usually denoted by Δx (x2-x1) and change in time is denoted by Δt (t2-t1).

13. Speed :--Speed in Physics is the distance covered by an object in unit time.
In other words, the rate at which the object is moving is called speed.
Unit time may be a second, an hour, a day, or a year.
It tells us how fast or slow an object is moving.
Speed is the scalar Quantity.
SI unit of speed is m/s.
Other units like kilometer per hour, miles per hour, feet per second are also used.
Here S is the distance covered by the object, V is its speed, and t is the time taken by it.
S = d / t
Dimensional formula is M0L1T-1

14. 1)Uniform Speed:--The body has uniform speed if it covers equal distances in
equal intervals of time however short the interval may be.
In the equation, S=v. t
v is the average speed of a body during time t. It is because the speed of the body may be
changing during the time interval t
2)Non Uniform Speed:-“A body does not have uniform speed if it does not cover
the equal distance with an equal interval of time.”
3)Average Speed :- Average speed is defined as the ratio of Total distance travelled to the
Total time taken.
Average Speed = Total Distance travelled /Total time taken
4)Instantaneous Speed :- When a body is moving with variable speed then the speed of a
body at any instant of time is called instantaneous speed.
s = ds/ dt
The speedometer of an automobile indicate its instantaneous speed.

15. Velocity :- The rate of change in position or displacement of an object with time is called the
velocity of that object.
Velocity = Displacement/ Time
1)Uniform Velocity :- An object could have uniform velocity if it covers equal displacement
in equal interval of time.
2) Non-Uniform Velocity :- A body said to be move with non-uniform velocity if it covers
unequal displacement in equal interval of time.
3)Average Velocity :- Average velocity is defined as ratio of total Displacement to the total
time taken.
Average Velocity = Total Displacement /Total time taken
4)Instantaneous Velocity :- Instantaneous of a particle is defined as the velocity of a
particle at any instant of time. V = dx/ dt

16. Velocity :--
“The rate of displacement of a body is called its velocity.”
The velocity tells us not only the speed of a body but also the direction along which the body is
moving.
The velocity of a body is a vector quantity.
It is equal to the displacement of a body in unit time. And is represented as:
Velocity = displacement / time
V = d/t
SI unit of velocity is the same as speed i.e., meter per second.
1)Non Uniform velocity:-“A body has uniform velocity if it dose not covers equal displacement in
equal intervals of time.
2)Uniform velocity:-“A body has uniform velocity if it covers equal displacement in equal intervals of
time however short the interval maybe.”In equation( d=v .t ) v is the average velocity of a body
during time t . It is because the velocity of the body may be changing during the time interval.
However, in many cases, the speed and direction of a body do not change. In such a case the body
possesses uniform velocity. That is the velocity of a body during any interval of time has the same
magnitude and direction.
3) Average velocity:-- is the total displacement covered in any direction in a total interval of time.” or
ratio of total displacement to time.

17. Acceleration :- The rate of change of velocity of an object with time is called the acceleration
of a body.
Acceleration = Change in Velocity /Time taken
1)Average Acceleration :- Average acceleration is defined as the change in velocity of a
body divided by total time taken.
Average acceleration = v/ t
2) Instantaneous acceleration :- It is defined as the acceleration of an object at any
instant of time during its motion.
Instantaneous acceleration = dv /dt
3)Uniform acceleration :- The motion of a body whose acceleration is constant is known as
uniformly accelerated motion.
4) Non-Uniform acceleration :- The motion of an object having variable acceleration is
known as non-uniform accelerated motion.
4) Instantaneous velocity :- It is defined as the velocity of an object at any instant of time
during its motion.
Instantaneous velocity = ds /dt

19. Distance Displacement
It is a magnitude that measures
the length that is traveled by an
object from one point to another.
It is a magnitude that measures
the variation of the position of a
body between two points,
considering a starting point and an
endpoint.
It is considered a scalar
magnitude.
It is considered a vector
magnitude.
It depends on the path that the
object follows.
It does not depend on the path
that the object follows.
It is expressed by a number and a
unit of magnitude frequently in
meters.
In physics, it is expressed by a
module (value), unity, direction,
and meaning.
It is obtained from the sum of all
the lengths traveled by an object.
It is obtained from the difference
in the length value of an endpoint
and an initial point of an object.
Difference between Distance and Displacement

20. Speed Velocity
Speed is the distance covered
by a body
in unit time.
Velocity is the
displacement covered by
a body in a unit time.
It is a scalar quantity. It is a vector quantity.
It Determines “How fast an
object
is moving”?
It determines “In which
direction an object is
moving”?
It indicates the rapidity of
objects.
It indicates both the
rapidity and position of
the object.
It is the rate of change of
distance.
It is a rate of change of
displacement.
It cannot be negative.
The velocity of moving
Objects can be negative,
positive or can be zero.
Difference between speed and velocity

21. Average Velocity and Average Speed :--

23. 1S T EQUATION OF MOTION
Consider an object which is moving along a straight line
path with uniform acceleration .
u= initial velocity of object velocity at time t=0 .
v= velocity of object after time t.
S= displacement covered by the object in time t.
The velocity time graph of the object is represented by
the line OB
acceleration =change in velocity
Total time taken
a = BA
DA
a = CD
OC
a = OD-OC
OE
a = v-u
t
v = u + at

24. SECOND EQUATION OF MOTION
Consider an object which is moving along a straight line path with
uniform acceleration .
u= initial velocity of object velocity at time t=0 .
v= velocity of object after time t.
S= displacement covered by the object in time t.
The velocity time graph of the object is represented by the line OB
Distance = area of trapezium [shown ingraph]
Distance or s = ½ (OD+BE) xh
s = ½ (u+v)x t
s = ½(u+u+at) x t [v = u+at by 1st of equation motion]
s = ½ (2u+at) x t
s=ut+½at2

25. THIRDEQUATION OF MOTION
Consider an object which is moving along a straight line path with
uniform acceleration .
u= initial velocity of object velocity at time t=0 .
v= velocity of object after time t.
S= displacement covered by the object in time t.
The velocity time graph of the object is represented by the line OB
Distance = area of trapezium [shown ingraph]
Distance or s =½ (OD+BE or BE+OD) x h
s = ½ (v+u) x t
s = ½ (v+u) x v-u [v =u+at then t = v-u ]
a a
s=(v2-u2)/2a
2as=(v2-u2)