L. R. & S. M. VISSANJI ACADEMY
SECONDARY SECTION - 2016-17
PHYSICS - GRADE: VII
MOTION
REST: A body is said to be at rest if it does not change its position with respect to a
fixed point in its surrounding.
MOTION: A body is said to be in state of motion, if its position changes with time,
with respect to its surroundings.
REST AND MOTION ARE RELATIVE TERMS:
For defining the term ‘Rest’ and ‘Motion’, we need some ‘surroundings’ or ‘reference
object’. An object may be in a position of rest with respect to one reference object,
and in motion with respect to another.
Suppose, you are travelling by a train, if you compare your position in relation to
other passengers or walls of the train, your position is fixed and you are at rest. But,
if you compare your position in relation to the platform or ground, you are in motion.
Mostly, we consider the motion of the objects with respect to the earth. Your house is
at rest as compared to the earth. But, the earth is continuously moving around the
sun. It means your house is also in motion along with the earth around the sun.
Thus, rest and motion are relative terms.
TYPES OF MOTION:
1. TRANSLATORY MOTION: If an object moves in a line in such a way that every
point of the object moves through the same distance in the same time, then the
motion of the object is called Translatory Motion.
They are of two types:
I.
RECTILINEAR MOTION: If an object moves along a straight line, its motion is
called Rectilinear Motion. It is also called as Linear Motion.
e.g. A boy running straight on a road is in Rectilinear Motion
e.g. A child sliding down a slide.
e.g. A freely falling stone.
II.
CURVILINEAR MOTION: If an object moves along a curved path or circular
path, its motion is called Curvilinear Motion.
e.g. A football kicked by a player moves in Curvilinear Motion.

CIRCULAR MOTION
Circular Motion is a special case of Curvilinear Motion.
The motion of a body along a circular path is called Circular Motion.
e.g. Motion of the moon around the earth.
e.g. Whirling of a stone tied to a string.
2. ROTATORY MOTION: If an object moves about a fixed axis or a fixed point,
without changing its position on the whole, then the object is said to be in
Rotatory Motion.
e.g. A Spinning charkha
e.g. the motion of the blades of an electric fan.
e.g. Spinning motion of the earth about its axis.
e.g. A merry-go-round.
e.g. A moving potter’s wheel.
3. OSCILLATORY MOTION: If an object moves to and fro about its mean position,
then the object is said to be in Oscillatory Motion.
e.g. Movement of a Simple Pendulum.
e.g. Motion of a swing.
e.g. Movement of the needle of a sewing machine.
4. VIBRATORY MOTION: The motion of an object in which only a part of the object
moves to and fro about its mean position, while the remaining object remains
fixed, is called Vibratory Motion.
Vibratory Motion is a special case of Oscillatory Motion.
e.g. When the string of a sitar
5. PERIODIC MOTION: The motion which gets repeated after regular intervals of
time is called Periodic Motion.
e.g. Motion of the hands of a clock.
e.g. Vibrations of strings of musical instruments.
e.g. Heartbeat and pulse of a normal person.
6. NON-PERIODIC MOTION: The motion which does not repeat itself after regular
interval of time is called Non=periodic Motion.
e.g. A man walking in a park.
e.g. Motion of an athlete
e.g. Motion of a vehicle on a busy road.
In some cases, the motion may be repetitive but may not be periodic.
e.g. Motion of lungs while breathing.
e.g. Swinging of arms while walking.
e.g. Motion of a rolling cricket ball on the ground.
These are repetitive in nature but are Non-periodic.
7. MULTIPLE MOTION: If a body exhibits more than one motion at the same time,
then such a motion is called Multiple Motion.
e.g. Motion of the earth: the earth rotates on its own axis as well as revolves
around the sun.
8. ROLLING MOTION: The motion in which a body undergoes both Translatory as
well as Rotatory Motion is called Rolling Motion.
e.g. The movement of a bicycle wheel
e.g. Movement of a drill machine.
9. RANDOM MOTION: When an object has no specific path and frequently changes
its motion, the motion is called Random Motion.
e.g. Motion of smoke particles
SCALAR QUANTITY AND VECTOR QUANTITY
SCALAR QUANTITY:
 A physical quantity which has only magnitude but no specific direction is called
Scalar Quantity.
 Scalar Quantity is specified by a number and a unit.
 Length, distance, area, volume, mass, time, energy and so on are the examples
of Scalar Quantities.
VECTOR QUANTITY:
 A physical quantity having magnitude as well as specific direction is called Vector
Quantity.
 A Vector Quantity is specified by a number, unit and direction.
 Displacement, Velocity, Force, Weight etc, are examples of Vector Quantity.
DIFFERENCE BETWEEN SCALAR QUANTITY AND VECTORY QUANTITY
1.
2.
Scalar Quantity
Scalar
quantities
have
only
magnitude.
They change if there magnitude
changes.
Vector Quantity
Vector Quantities have magnitude as
well as direction.
They change if either their magnitude,
direction or both change.
DISTANCE AND DISPLACEMENT
DISTANCE: The actual length of the path covered by a moving body is known as the
Distance covered by the body.
UNIT OF DISTANCE:
1. In S.I. System, the unit of distance is metre (m).
2. Other units are centimetre (cm) and kilometre (km).
Relation between metre (m) and centimetre (cm)
1m
=
100 cm
1 cm
=
1 .
100
10-2 m
=
Relation between kilometre (km) and metre (m)
1 km =
1000 m
1m
1 .
1000
=
=
10-3 m
DISPLACEMENT: The shortest distance between the initial position and the final
position in a particular direction is called as its Displacement.
UNIT OF DISPLACEMENT: Units of Displacement are same as Units of Distance.
DIFFERENCE BETWEEN DISTANCE AND DISPLACEMENT
1.
Distance
The actual length of the path
covered by a moving body is known
as the Distance covered by the
body.
Displacement
The shortest distance between the
initial position and the final position in a
particular direction is called as its
Displacement.
2.
It depends on the path followed by It does not depend on the path followed
the object.
by the object.
3.
It is always positive.
It can be positive, negative or zero.
4.
It is a Scalar Quantity.
It is a Vector Quantity.
5.
Its magnitude is equal to or greater Its magnitude is either equal to or less
than the magnitude of displacement. than the magnitude of distance
covered.
SPEED AND VELOCITY
SPEED: The distance travelled by a body per unit time is known as the Speed of the
body.
Speed is denoted by the symbol s.
FORMULA
Speed (s)
=
Distance travelled (d)
Time taken (t)
UNIT OF SPEED
1. In S.I. System, distance is measured in metres and time in seconds.
Therefore, S.I. Unit of speed is metre/second. It is written as m/s or m s-1 .
2. Sometimes, we used cm/s and m/min.
3. Long distances are measured in km/hr.
VELOCITY:
The distance travelled by a body per unit time in a given direction is called the
Velocity of the body.
OR
The displacement covered by the moving body per unit time is called the Velocity of
the body.
FORMULA
Velocity
=
Displacement
Time taken
UNIT OF VELOCITY
The S.I. Unit of velocity is metre per second (m/s)
DIFFERENCE BETWEEN SPEED AND VELOCITY
The S.I. Unit of velocity is same as that of speed. But, direction is to be specified
while expressing velocity of a body. Due to difference in direction, velocity can be
positive or negative.
Consider two cars running on a highway with a speed of 60 km/hr, one towards the
east and the other towards the west. Now, if we consider the velocity if the first car
as positive, then the velocity of the other car will be taken as negative.
If a person completes a journey such that his final position is same as its initial
position then his displacement is zero and hence his velocity is zero. It is to be noted
here that in this example, speed of the person has a finite value because he has
covered a definite distance. However, his velocity is zero.
1.
2.
3.
Speed
The distance travelled by a body per
unit time is known as the Speed of
the body.
It is a Scalar Quantity.
Speed of a moving body is always
positive.
Velocity
The distance travelled by a body per unit
time in a given direction is called the
Velocity of the body.
It is a Vector Quantity.
Velocity of a moving body can be
positive, negative or zero.