Monday, November 5, 2018
9th class physics Work, formula derivation of work,dependence of work,un...
Work
Definition:
work is done when a force acts ona body
and displace it int the direction of force
and displace it int the direction of force
Formula:work is the product of force and displacement in the direction of
force
force
W= F S
Unit:
Joule or Nm or kg m2 s-2
Joule or Nm or kg m2 s-2
quantity: work Is a Scalar quantity
work
done when force and displacement are not along same line :
done when force and displacement are not along same line :
Sometimes force and displacement do not have the
same direction
such as shown in figure
same direction
such as shown in figure
Here the force F
is
making an angle
θ with
the surface on which
Work done by a force inclined with the
displacement.
the body
is moved.
is
making an angle
θ with
the surface on which
Work done by a force inclined with the
displacement.
the body
is moved.
Resolving F into its perpendicular components Fx and Fy as
Fx= F
Cos θ
Cos θ
Fy= F Sin θ
when force and displacement are not along the
same line then horizontal component of the force is taken
same line then horizontal component of the force is taken
Fx= F
Cos θ
Cos θ
W=Fx S
W=F Cos θ S
W=F S Cos θ
W=F S Cos θ
Dependence
of work
of work
work depends upon the following factors
•force
•Displacement
•angle
between force and displacement
between force and displacement
Unit
of work
of work
SI unit of work is joule (J). It is
defined as
defined as
Joule
The amount of work is one joule when a
force of one newton displaces a body through one metre in the direction of force.
force of one newton displaces a body through one metre in the direction of force.
Thus 1 J = 1 N x 1m
Joule is a small unit of work. Its bigger
units are:
units are:
1 kilo joule (1kJ) = 1000 J = 103 J
1mega joule (1MJ) =1000 000 J =10 6J
Sunday, November 4, 2018
physics 9th class Variation of g with altitude,altitude
Gravitational
field of earth
field of earth
According to the Newton’s law of
gravitation, the gravitational force between a body of mass m and the Earth is
given by
gravitation, the gravitational force between a body of mass m and the Earth is
given by
where Me is the mass of the Earth and r
is the distance of the body from the center of the Earth
is the distance of the body from the center of the Earth
•The weight of a body is due to the
gravitational force with which the Earth attracts a body
gravitational force with which the Earth attracts a body
•There is a field which exist all around
the earth which attracts the body toward the centre of earth this field is called
gravitational field of earth
the earth which attracts the body toward the centre of earth this field is called
gravitational field of earth
•As we go away from centre of
earth gravitational field decrease
earth gravitational field decrease
FIELD
FORCE
FORCE
Definition:
Non-contact force between bodies is
called field force
called field force
For Example gravitational pull of the
earth
earth
The velocity of a body, thrown up, goes
on decreasing while on return its velocity goes on increasing. This is due to
the gravitational pull of the Earth acting on the body whether the body is in
contact with the Earth or not. Such a force is called the field force.
on decreasing while on return its velocity goes on increasing. This is due to
the gravitational pull of the Earth acting on the body whether the body is in
contact with the Earth or not. Such a force is called the field force.
GRAVITATIONAL
FIELD STRENGTH:
FIELD STRENGTH:
In the gravitational field of the Earth,
the gravitational force per unit mass is called the gravitational field
strength of the Earth.
the gravitational force per unit mass is called the gravitational field
strength of the Earth.
At
any place its value is equal to the value of g at that point.
any place its value is equal to the value of g at that point.
Near the surface of the Earth, the
gravitational field strength is 10 N kg-1.
gravitational field strength is 10 N kg-1.
physics 9th class satellites, GPS, communication satellite,geostationary...
SATELLITE
An object that revolves around the planet
is called a satellite.
is called a satellite.
Natural
satellite
satellite
Natural object which revolve around some
planets is called natural satellite
planets is called natural satellite
i.e The
moon revolves around the Earth so moon is a natural satellite of the Earth
moon revolves around the Earth so moon is a natural satellite of the Earth
Artificial
Satellite
Satellite
Scientists have sent many objects into
space. Some of these objects revolve around the Earth. These are called
artificial satellites. Most of the artificial satellites, orbiting around the
Earth are used for communication purposes.
space. Some of these objects revolve around the Earth. These are called
artificial satellites. Most of the artificial satellites, orbiting around the
Earth are used for communication purposes.
GPS
Global Positioning System (GPS) is a
satellites navigation system. It helps us to find the exact position of an
object anywhere on the land, on the sea or in the air. GPS consists of 24
Earth satellites. These satellites revolve around the Earth twice a day with a
speed of 3.87
km s-1.
satellites navigation system. It helps us to find the exact position of an
object anywhere on the land, on the sea or in the air. GPS consists of 24
Earth satellites. These satellites revolve around the Earth twice a day with a
speed of 3.87
km s-1.
Geostationary
satellite
satellite
Geostationary satellites orbit around the
earth at a altitude of 42300
km. their
velocity with respect to earth is zero so they appear stationary with respect
to earth so they are known as Geostationary satellites
earth at a altitude of 42300
km. their
velocity with respect to earth is zero so they appear stationary with respect
to earth so they are known as Geostationary satellites
Geostationary satellites are used for
communication
communication
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