MOTION
What is motion ?
What are the different types of motion?
What is the physics relating to motion called?
ok! we have answers to all these questions.
1. what is motion?
when a body is continuously
changing its position with
respect to the surroundings
, then we say that the body
is in motion.
EXAMPLE
1.When an athlete is running on the ground
then he is continuously changing his position
with respect to the audience who are sitting
at rest.
2.We are continuously changing our position
since morning till night with respect to
earth which is at rest.
3.The earth is continuously changing position
with respect to sun which is at rest.
object in motion?

If you are standing in one place, and your friend walks
by you, are you moving relative to your friend?
◦ Is your friend moving relative to you?
◦ Is either of you moving relative to the earth?
Answer:
You are moving relative to your friend, and
your friend is moving relative to you!
 You (the Joker) are not moving relative to the
earth, but your friend is. You are both moving
relative to the sun!
Who is moving
relative to the
computer
screen?

2.What are the different types
of motion?
Linear motion : when a body moves either in
a straight line or along a curved path, then we
say that it is executing linear motion.
1. when a body moves in a straight line then the
linear motion is called rectilinear motion.
eg ., an athlete running a 100 meter race
along a straight track is said to be a linear
motion or rectilinear motion.
2.when a body moves along a curved path then
the linear motion is called curvilinear
motion. eg., a planet revolving around its
parent star
Other types of motion
are :
Rotatory motion : A body is said
to be in rotatory motion when it
stays at one place and turns round
and round about an axis. example :a
rotating fan, a spinning top, the
earth.
Oscillatory motion : a body is
said to be in oscillatory motion
when it swings to and fro about a
mean position.
example : the pendulum of a clock,
the swing etc.,
Vibratory motion
When a certain part of a body always
remains fixed and the rest of the
body moves to-and-fro in a definite
style, then its motion is called
vibratory motion.
Periodic motion
A motion which repeats itself
at regular interval of time is
called periodic motion.
Multiple motion
When an object possesses two or more types
of motions at the same time, then such a
motion is called multiple motion.
examples:
When a spin bowler delivers a ball, the ball has
a motion of spin(rotatory motion)while it
moves toward the batsman(translatory motion).
SIMPLE PENDULUM AND
RESTORING FORCE
PERIODIC MOTION

The motion which
repeats itself after
fixed time intervals
is called periodic
motion
The best example of periodic motion are the pendulum clocks.
A SIMPLE PENDULUM

A string with a mass at
the end which is free to
swing is called a
pendulum.
TO AND FRO MOTION
The ball moves to
and fro. It rises to
extreme positions
on both sides and
reverses its motion
 Oscillations
gradually die down

LENGTH OF THE PENDULUM

The length of the string
from the point of
suspension to the mass
is called the length of
the pendulum.

It is denoted by L
MEAN POSITION OF THE PENDULUM
The central position
of the pendulum (the
starting position) is
called the mean
position
of
the
pendulum.
 It is labeled here as
B.

EXTREME POSITIONS OF THE
PENDULUM

A and C are the extreme positions of the
pendulum.
OSCILLATION

The motion of the
mass from its extreme
position A to C and
back to A is called an
oscillation.
TIME TAKEN FOR ONE OSCILLATION
The time taken for one oscillation is very
short and therefore, difficult to measure
accurately.
 To find the time taken, we find the time
taken for large number say 20 oscillations.
This time divided by 20 will give us time
taken for one oscillation.

PERIODIC TIME OF THE SIMPLE
PENDULUM

The time taken to complete one
oscillation is called the periodic time of
the simple pendulum.

It is sometimes also called its period and
is denoted by T.
RELATIONSHIP BETWEEN T AND L

The equation is
The Period of the pendulum T is related to the length L
by the relation
L
T  2
g
Factor affecting Time period
of simple of pendulum

Time period of
 Time period of
simple pendulum
simple pendulum
depend on length
does not depend on
and acceleration due mass of bob and
to gravity (g)
material of bob
SCALARS AND VECTORS
The motion of objects can be described by words - words
such as distance, displacement, speed, velocity, and
acceleration. These mathematical quantities which are used
to describe the motion of objects can be divided into two
categories. The quantity is either a vector or a scalar. These
two categories can be distinguished from one another by
their distinct definitions:
Scalars are quantities which are fully described by a
magnitude alone. Eg: distance , mass ,time ,volume etc
Vectors are quantities which are fully described by both a
magnitude and a direction.
Eg :displacement , velocity , force ,acceleration etc.,
DISTANCE
Distance is the actual path
covered by a body, irrespective
of its direction. Hence, it is
scalar quantity.
Displacement
Displacement is shortest distance
travelled by a body from its initial
position to its final position in
particular direction Hence , it is a
vector quantity. It indicates the
change in position of a body.
Therefore, has both length and
direction
Here’s a problem (or two)…..
If the earth spins on its axis at 1100 miles/hour,
what is the speed of the Earth's rotation in feet
per second?
The earth travels at 68,000 miles/hour as it
moves around the sun. How many miles does the
earth travel in one trip around the sun?
Speed
Speed is the distance traveled in a given amount of
time
Speed=distance
time
The units for speed:
meters/second (m/sec)
kilometers/hour (km/hr)
Speed that does not change is constant speed
Speed

Speed = Distance
time
s=d
t
Example: A car travels 450km in 5 hours.
What is the speed of the car?
Answer:
 Speed
= distance
time
 Speed = 450 Km
5 hours
 Speed = 90km
hr
More practice
 1.
How far can a plane travel if it flies
800km/hr for 9 hours?
 2.
How long does it take a ship to go
500 km if it travels at a speed of
50km/hr?
1. Answer
Then: d = s t
800km
hr
9hr = 7200km
2.Answer
And then: since s = d
t
t= d
s
500km 1hr
= 10hrs
50km
Velocity
velocity is the rate of change of the position of an
object, equivalent to a specification of its speed and
direction of motion.
Speed describes only how fast an object is moving,
whereas velocity gives both how fast and in what
direction the object is moving.
If a car is said to travel at 60 km/h, its speed has been
specified. However, if the car is said to move at 60 km/h
to the north, its velocity has now been specified. To have
a constant velocity, an object must have a constant
speed in a constant direction.
Velocity
 Speed
 What
in a given direction.
is the velocity of a boat that
travels from St. Peter to Mankato
(10 miles) in 15 minutes?
Answer
 Speed
= distance = 10miles
time
15min
 Speed = 0.6666667 mil = 0.7 mil
min
min
Change your answer to mi/hr!
 0.67mi
min
 40
mi
hr
60min =
hr
Velocity can be classified as
uniform and variable velocity
Uniform velocity :- If a body
travels with a uniform speed in a
constant direction, then the
body is said to have uniform or
constant velocity
Variable velocity :- we normally
come across variable velocities of
moving bodies, Which means speed
or direction or both speed and
direction of moving bodies change
constantly
Speed
velocity
It is the rate of
 It is the rate of change
change of distance
of displacement
 It is a scalar quantity  It is a vector quantity
 speed of moving
 The velocity of a
body cannot be zero
moving body become
zero if it return to its
initial position.

Acceleration
The change in velocity is Acceleration
Acceleration is measured in m/sec2
Formula is:
final velocity – original velocity
time taken
Uniform and nonuniform
acceleration
Acceleration can be uniform or nonuniform. Nonuniform acceleration
requires
a change in acceleration. For example, when you’re driving, you encounter
stop signs or stop lights often, and when you decelerate to a stop and then
accelerate again, you take part in nonuniform acceleration.
Other accelerations are very uniform (in other words, unchanging), such as
the acceleration due to gravity on the surface of the earth. This acceleration
is 9.8 meters per second2 downward, toward the center of the earth, and it
doesn’t change (if it did, plenty of people would be pretty startled).
ACCELERATION

Problem:
A car is moving in a straight line it speed up
from 65km/hr to 74km/hr, in .17hrs What is the car’s
acceleration.

Acceleration = Vf –Vi 1
t
74kmf – 65kmi
hr
hr
1
= 53 km/hr2
0 .17hr
ACCELERATION!!!

Problem: Suppose a car moving in a
straight line steadily increases its
speed each second. First from 35 to
40 km/hr, then from 45 to 50 km/hr.
What is its acceleration?
Answer


15km 1h
1min 1 = .001 km
hr 60 min 60 sec 3
sec2
DEACCELERATION
Deceleration ( “negative”
acceleration):
 A term commonly used to mean a
decrease in speed.
 Acceleration in a direction opposite to
the direction of travel.
 Deceleration is negative acceleration and
has a negative value to indicate direction.

Relation between uniform
acceleration and time

Suppose body start with initial velocity of
u m/s , Now body go on increasing its
velocity by an amount a uniformly , let its
final velocity be v m/s after a time of t sec
a = final velocity – original velocity
time take
= (v-u)/t
Or v= u + at
This is called equation of motion