KINEMATICS
KINEMATICS
MOTION IN ONE DIMENSION
IMPORTANT TERMS 2.3 Rest and Motion are relative
Rest and motion depends upon the observer. The object in
1. MECHANICS one situation may be at rest whereas the same object in
another situation may be in motion.
,t is the branch of Physics, which deals with the study of
motion of physical bodies. The driver of a moving car is in motion with respect to an
observer standing on the ground whereas, the same driver is at
Mechanics can be broadly classified into following branches rest with respect to the man(observer) in the passengers seat.
1.1 Statics 3. WHILE STUDYING THIS CHAPTER
It is the branch of mechanics, which deals with the study of We will treat the objects as Point mass object
physical bodies at rest. x An object can be considered as a point mass object if
during the course of motion it covers distances much
1.2 Kinematics
greater than its own size.
It is the branch of mechanics, which deals with study of We shall confine ourselves to the study of rectilinear motion
motion of physical bodies without taking into account the x Rectilinear motion is the study of motion of objects along
factors, which causes motion. a straight line.
1.3 Dynamics 4. POSITION, DISTANCE, DISPLACEMENT
It is the branch of mechanics, which deals with the study of 4.1 Position
motion of physical bodies taking into account the factors
which causes motion. x Position of an object is always defined with respect to
some reference point which we generally refer to as origin.
2. REST AND MOTION
x To define the change in position we have two physical
quantities
2.1 Rest
4.2 Distance
x An object is said to be at rest if it does not changes its
position with respect to the surrounding. x It is the actual path traversed by the body during the
course of motion
x The white board in the classroom is at rest with respect
x SI unit is ‘m’
to the classroom
x Dimensions [M0L1T0]
2.2 Motion
4.3 Displacement
x An object is said to be in motion if it changes its position x It is the difference between the final and initial positions
with respect to the surrounding. of the object during the course of motion
x When we walk, run or ride a bike we are in motion with x SI unit is ‘m’
respect to the ground. x Dimensions [M0L1T0]
, KINEMATICS
Difference between Distance and Displacement
Distance Displacement
It is the actual path traversed by the object during It is the difference between the initial and the final positions
the course of motion 'x x2 – x1 where, x2 and x1 are final and initial
position respectively
It is a scalar quantity It is a vector quantity
The distance travelled by an object during the course of The displacement of an object may be positive,
motion is never negative or zero and is always positive negative or, zero during the course of motion
The distance travelled is either equal or greater The magnitude of displacement is less than or equal
than displacement and is never less than magnitude to the distance travelled during the course of motion
of displacement Distance t _Displacement_
The distance depends upon the path travelled The magnitude of displacement is independent of the
path taken by an object during the course of motion
Difference between Speed and Velocity
Speed Velocity
It is defined as the total path length travelled divided by It is defined as the change in position or displacement
the total time interval during which the motion has taken divided by the time intervals, in which displacement
place occurs of
It is a scalar quantity It is a vector quantity
It is always positive during the course of the motion It may be positive, negative or zero during the course of
the motion
It is greater than or equal to the magnitude of velocity It is less than or equal to the speed
NOTE Example:- mass, length, time, distance, speed, work,
temperature
If the motion of an object is along a straight line and in the
same direction, the magnitude of displacement is equal to the 5.2 Vector quantities
total path length. In that case, the magnitude of average
velocity is equal to the average speed. This is not always the The physical quantities which have magnitude as well
case. The average velocity tells us how fast an object has as direction, are called vector quantities.
been moving over a given interval but does not tell us how Example:- displacement, velocity, acceleration, force,
fast it moves at different instants of time during that interval. momentum, torque
5. SCALAR AND VECTOR QUANTITIES 6. AVERAGE VELOCITY AND AVERAGE SPEED
5.1 Scalar quantities 6.1 Average velocity
The physical quantities which have only magnitude but x It is defined as the change in position or
no direction, are called scalar quantities. displacement divided by the time intervals, in which
KINEMATICS
MOTION IN ONE DIMENSION
IMPORTANT TERMS 2.3 Rest and Motion are relative
Rest and motion depends upon the observer. The object in
1. MECHANICS one situation may be at rest whereas the same object in
another situation may be in motion.
,t is the branch of Physics, which deals with the study of
motion of physical bodies. The driver of a moving car is in motion with respect to an
observer standing on the ground whereas, the same driver is at
Mechanics can be broadly classified into following branches rest with respect to the man(observer) in the passengers seat.
1.1 Statics 3. WHILE STUDYING THIS CHAPTER
It is the branch of mechanics, which deals with the study of We will treat the objects as Point mass object
physical bodies at rest. x An object can be considered as a point mass object if
during the course of motion it covers distances much
1.2 Kinematics
greater than its own size.
It is the branch of mechanics, which deals with study of We shall confine ourselves to the study of rectilinear motion
motion of physical bodies without taking into account the x Rectilinear motion is the study of motion of objects along
factors, which causes motion. a straight line.
1.3 Dynamics 4. POSITION, DISTANCE, DISPLACEMENT
It is the branch of mechanics, which deals with the study of 4.1 Position
motion of physical bodies taking into account the factors
which causes motion. x Position of an object is always defined with respect to
some reference point which we generally refer to as origin.
2. REST AND MOTION
x To define the change in position we have two physical
quantities
2.1 Rest
4.2 Distance
x An object is said to be at rest if it does not changes its
position with respect to the surrounding. x It is the actual path traversed by the body during the
course of motion
x The white board in the classroom is at rest with respect
x SI unit is ‘m’
to the classroom
x Dimensions [M0L1T0]
2.2 Motion
4.3 Displacement
x An object is said to be in motion if it changes its position x It is the difference between the final and initial positions
with respect to the surrounding. of the object during the course of motion
x When we walk, run or ride a bike we are in motion with x SI unit is ‘m’
respect to the ground. x Dimensions [M0L1T0]
, KINEMATICS
Difference between Distance and Displacement
Distance Displacement
It is the actual path traversed by the object during It is the difference between the initial and the final positions
the course of motion 'x x2 – x1 where, x2 and x1 are final and initial
position respectively
It is a scalar quantity It is a vector quantity
The distance travelled by an object during the course of The displacement of an object may be positive,
motion is never negative or zero and is always positive negative or, zero during the course of motion
The distance travelled is either equal or greater The magnitude of displacement is less than or equal
than displacement and is never less than magnitude to the distance travelled during the course of motion
of displacement Distance t _Displacement_
The distance depends upon the path travelled The magnitude of displacement is independent of the
path taken by an object during the course of motion
Difference between Speed and Velocity
Speed Velocity
It is defined as the total path length travelled divided by It is defined as the change in position or displacement
the total time interval during which the motion has taken divided by the time intervals, in which displacement
place occurs of
It is a scalar quantity It is a vector quantity
It is always positive during the course of the motion It may be positive, negative or zero during the course of
the motion
It is greater than or equal to the magnitude of velocity It is less than or equal to the speed
NOTE Example:- mass, length, time, distance, speed, work,
temperature
If the motion of an object is along a straight line and in the
same direction, the magnitude of displacement is equal to the 5.2 Vector quantities
total path length. In that case, the magnitude of average
velocity is equal to the average speed. This is not always the The physical quantities which have magnitude as well
case. The average velocity tells us how fast an object has as direction, are called vector quantities.
been moving over a given interval but does not tell us how Example:- displacement, velocity, acceleration, force,
fast it moves at different instants of time during that interval. momentum, torque
5. SCALAR AND VECTOR QUANTITIES 6. AVERAGE VELOCITY AND AVERAGE SPEED
5.1 Scalar quantities 6.1 Average velocity
The physical quantities which have only magnitude but x It is defined as the change in position or
no direction, are called scalar quantities. displacement divided by the time intervals, in which
