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9th Class Chapter 5 Physics Short Questions

An important facility for 9th class students preparing for short questions physics 9th class chapter 5 of BISE. Get hundreds of questions to prepare and get better marks in 9th physics

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Question: 1
Explain the law of gravitation.
1-82
Every body in the universe attracts every other body with a force which is directly proportional of the product of their masses and inversely proportional to the square of the distance between their centers.
Question: 2
What is meant by the force of gravitation?
2-82
The force with which everybody in the universe attract another body towards itself is called gravitational force.
Question: 3
What is Satellite?
3-82
Satellite an object that revolves around a planet is called a satellite. Example: The moon revolves around teh Earth so moon is a natural satellite of the Earth.
Question: 4
Does an apple attract the Earth towards it?
4-82
Yes, according to law of law of gravitation, apple attracts the earth.
Question: 5
Define artificialsatellite?
5-82
Man made objects moving in fixed circular orbits around the Earth .
Question: 6
Who is the first man who gave the idea of gravity?
6-82
The first man who came up with the idea of gravity was is99c newton.
Question: 7
What is meant by gravitational field strength?
7-82
In the gravitational field of the earth, the gravitational force per unit mass is called the gravitational field strength of the earth.
Question: 8
What is meant by geostationary orbit?
8-82
Communication satellites take 24 hours to complete its one rotation around Earth, As Earth also complete its one rotation about its axis in 24 ours hence these communication satellites appear to be stationary with respect to Earth.So the orbits of such satellites are called as geostationary orbits.
Question: 9
What is meant by the force of gravitation
9-82
Gravitational force: The force with which everybody in the universe attracts another body toward its self is called gravitational force. OR the force with which earth attract the objects toward us centre
Question: 10
Define orbital velocity.
10-82
The velocity of the satellite in its orbit is called orbital velocity.
Question: 11
Why earlier scientists could not guess about the gravitational force?
11-82
Earlier scientists could not guess about the gravitational force because the concept of gravitation was first of all given by newton in 1665 earlier and scientist could not guess because there was no concept of gravitation
Question: 12
Why communication satellites are geostationary satellite?
12-82
Communication satellites take 24 hours to complete their one revolutionaround the earth. As earth also completes it's one rotation about it'saxis in24 hour, hence these communication satellites appear to be stationary with respectof Earth
Question: 13
How Newton's law of gravitation helps in understanding the motion of satellites
13-82
Satellites require centripetal force to orbit around the Earth. This centripetal force provided to satellite by gravitational force of Earth according to Newton's law of gravitation.
Question: 14
What are artificial satellites?
14-82
Scientist have sent many objects into space, Some of these objects revolved around the earth. These are called artificial satellites.
Question: 15
Do you attract the Earth or earth attracts you?
15-82
You attract the earth with the same force that the earth attracts you. However, this force has more effect on you because you are much lighter than Earth.
Question: 16
With what force an apple weighing 1 N attract the Earth?
16-82
According to Newton's law of gravitation apple attract the Earth with a force of 1 N.
Question: 17
Can you determine the mass of our moon? If yes, then what do you need to know?
17-82
Yes mass of our moon can be determinedby using law of gravitation. We have to know the value of G, The gravitational acceleration g on moon and the radius of moon.
Question: 18
Every body has weight in Earth's gravitational field. why?
18-82
Weight of a body in Earth's gravitational field is due to the gravitational force between the body and the earth.
Question: 19
What is meant by GPS
19-82
GPS: Global positioning system (GPS) is a satellite navigation system GPS consist of 24 Earth satellites It helps us to find the exact position of an object on the land on the sea or in the air
Question: 20
Why earlier scientists could not guess about the gravitational force
20-82
Earlier scientists could not realize the force between two masses because it is of very small value it could e detected only by very sensitive instruments which were not invented in old ages.
Question: 21
What is meant by force of gravitation?
21-82
The force due to which everybodyof the universe attracts every other body is called force of gravitation
Question: 22
What is gravitational field?
22-82
"The space around the Earth in which another object feels the earth's gravitational force called gravitational field. Its direction is towards centre of Earth.
Question: 23
Define Natural satellite?
23-82
The moon revolves around the Earth as moon a natural satellite
Question: 24
With what force an apple weighting 1 N attracts the Earth.
24-82
Due to Newton's third law of motion , an apple attracts the Earth with an equal magnitude that the Earth attracts the apple with and the type of force is gravitational.
Question: 25
Explain the law of gravitation
25-82
Law of Gravitation: Every body in the universe attracts every other body with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centrer
Question: 26
Do you attract the Earth or the Earth attracts you
26-82
We and earth both attract each other. Since the mass of Earth is very large, it attracts nearby objects with a significant force
Question: 27
What is a field force?
27-82
Field force; Such a force which act on a body by another body without any physical contact is called field force.
Question: 28
What is a field force
28-82
Such a force which act on a body by another body any physical contact is called field force
Question: 29
Write equation to determine mass of earth
29-82
Mass of earth can be determine by formula
M=R/g
and its value is M=6*10 kg
Question: 30
What is GPS?
30-82
Global positioning system (GPS) is a satellite navigation system. It helps us to find the exact position of an object anywhere on the land on the sea or in the air.
Question: 31
Why don't we feel the force of gravitation between objects around us in daily life
31-82
Due to small value of g the gravitational force of attraction between objects around us is very small and we do not feel it.
Question: 32
Why we can not feel gravitational force around us
32-82
Due to small value of the gravitational force of attraction between object around us is very small and we do not feel it.
Question: 33
What do you known about G
33-82
G is a constant It called gravitational constant Its value is same every where.
Question: 34
How Newton's law of gravitation helps in understanding the motion of satellites?
34-82
A satellite requirescentripetal force that keeps it to move around the earth. The gravitational force of attraction between the satellite and the earth provides the necessary centripetal force.
Question: 35
How the mass of Earth can be dtermined
35-82
Mass of Earth can be determined by Newton's law of gravitation. Mass of earth is determined by following formula
n=rg/g
Question: 36
What is the height and speed of Geo stationary satellite from the surface of the earth
36-82
The height of a geostationary satellite is about 42300km from the surface of the Earth Its velocity with respect to Earth is zero
Question: 37
Define gravitational field
37-82
Gravitational Field
The space around the Earth in which another object feels the earth gravitational force called gravitational field Its direction is toward centre of Earth.
Question: 38
Does an apple attract the Earth toward it
38-82
yes, according to law of gravitation apple attracts the earth
Question: 39
Define force of gravitation.
39-82
Force of gravitation: The force due to which every body of the universe attracts every other body is called force of gravitation
Question: 40
On what factors the orbits speed of a satellite depends
40-82
Orbital speed of satellite depends upon following factors.
Height from earth surface
Gravitational aceleration
Question: 41
What is the numerical values of g at Sun and Mars
41-82
The value of g on Sun is 274.2
The value of g on mars is 3.73
The value of g on moon is 1.62ms
The value of g on earth is 9.8 ms
Question: 42
Why communication satellites are stationed at geostationary orbits
42-82
Communication satellites are stationed at geostationary orbit so that they always face the same side of the earth and dish antennas sending and receiving the signals from them have always fixed direction.
Question: 43
What is field force
43-82
The gravitational force acting on a object in gravitational field is called field force.
Question: 44
Give value and unit of G in gravitational law
44-82
Value of G in gravitational law is 6.673*10
Question: 45
What are artificial satellites
45-82
Scientist have sent many objects into space. Some of these objects revolved around the earth These are called artificial satellites.

Question: 46
Define orbital velocity
46-82
Orbital Velocity: The velocity of the satellite in its orbit is called orbital velocity
Note: Orbital velocity of satellite orbiting nearest to the earth surface is 8km
Question: 47
Why law of gravitation is important to us
47-82
Following points explain the importance of gravitational law
We can find mass of Earth with the help of gravitational law
We can understand the motion of satellites with the help of gravitational law of gravitation tells us that why artificial satellites orbit around the Earth.

Question: 48
Why communication satellites appear stationary with respect to Earth
48-82
When communication satellites are sent to space after some times, these satellites begin to revolve around the Earth and their speed becomes to the speed of the Earth Therefore communication satellites appears stationary with respect of Earth
Question: 49
What is a satellite
49-82
Satellite: An object that revolves around a planted is called a satellite

Question: 50
What is difference between g and G
50-82
Gravitational Acceleration: The value of acceleration due to gravity g depends on the radius of the earth
The value of g changes with respect to height for a body from the earth
Question: 51
Explain how the value of g varies with altitude
51-82
The value of g at height (h) from the earth surface is given by
G=G/M/(r+h)
Question: 52
The weight of an object is less a=on moutains as compared on sesa level
52-82
The value of g is less on mountains as compared to sea level therefore the weight of an object is also less on mountains as compared to sea level
Question: 53
Define geo stationery satellite
53-82
Geo-stationery Satellite: Such a satellite whose velocity is zero with respect to Earth is called geo-stationery satellite The height of geostationary satellite is about 42300 km from the Earth
Question: 54
What is the relation between the value of g and radius of Earth
54-82
As we know that: G=gm/r
Question: 55
Can you determine the mass of our Moon
55-82
Yes We can determine the mass of our Moon by Newton's law of gravitation
Question: 56
Write the values of Following
56-82
Radius of Earth Gravitational constant g Radius of Earth The value of Radius of Earth R is 6.4*10m
Question: 57
Why does the vale of g vary from place to place
57-82
The value of g is inversely proportional to the square of radius of earth A the radius of Earth vary from place to place so the value of g is also vary from lace to place
Question: 58
Define orbital velocity and write its formula
58-82
Orbital Velocity: The Velocity at which a body revolves about another body

Question: 59
Write the value and unit of gravitational constant G in SI units
59-82
Value In SI unit the value of G is
Unit: Nm kg
Question: 60
On which factors the value of g on any celestial object depends upon
60-82
Value of g on the surface of a celestial object depends on its mass and its radius
Question: 61
Define mass of earth
61-82
The quantity of matter in Earth is called Mass of Earth Its value is
Question: 62
Define Geostationary orbit
62-82
Geostationary orbit: An orbit in which Geostationary satellites travel is called Geostationary orbit
Question: 63
How can you say that gravitational force is a field force
63-82
When an object thrown upward it comes back to earth due to gravitational pull of Earth as Earth attract that object without any physical connection so the gravitational force is a field force.
Question: 64
What is the meant by communication satellite
64-82
Communication satellite: Satellites which was for commination are called communication satellites these are 423,00km away from surface of earth
Question: 65
What is meant by satellite
65-82
Satellites An object that revolves around a planet is called statellite
Question: 66
Does the weight of an apple increases decreases or remain constant when taken to the top of a mountain
66-82
When an apple is taken to the top of mountain its weight decreases because the value of g decreases on mountains
Question: 67
Define field force and gravitational field strength
67-82
Force Field: A force which is affect by a body due to any field is called force field
Question: 68
What is consistence of gravitational law with Newton's third Law
68-82
According to Newton's gravitational law the force of gravitation between two masses is equal in magnitude but opposite in direction which is exactly the same to Newton third law of motion
Question: 69
What is meant by global positioning system
69-82
Global Positioning System Global positioning System (GPS) is a satellites navigation system It help us to find the exact position of an object any where on the land on the sea or in the air GPS consists of 24 Earth a day with a speed
Question: 70
With what force an apple weighing 1 N attract the Earth
70-82
According to Newton law of gravitation apple attract the Earth with a force of 1N
Question: 71
What is the direction of gravitational field
71-82
The direction of gravitational field around the earth is always toward the centre of earth
Question: 72
What is orbital speed of a low orbit satellite
72-82
A satellite revolving around very close to the Earth, has speed V nearly 8kms
Question: 73
What is meant by geostationary orbit
73-82
Communication satellites take 24 hours to complete its one rotation around Earth As Earth also complete its one rotation about its axis in 24 hours hence these communication satellites appear to be stationary with respect to Earth So the orbits of such satellites are called as geostationary orbits
Question: 74
State the difference between natural and artificial satellites.
74-82
Artificial Satellites: Scientists have sent many objects into space Some of these objects revolve around the Earth These are called artificial satellites.
Question: 75
How can you say that gravitational force is a field force
75-82
Gravitational force can act on a body with and without contact fhere fore it is field force
Question: 76
Everybody has weight in Earth gravitational field
76-82
Weight of a body in Earth gravitational field is due to the gravitational force between the body and the Earth
Question: 77
Why is the value of g different at different place
77-82
Therefore it is clear that the value of g becomes one fourth if the height of object increases equal to Earth radius from Earth surface Similarly, the value of g becomes one nineth if the height of object increase equal to double of Earth radius from Earth surface Formula shows that the value of g at different heights will be different Due to this reason the value of g is different at different places.
Question: 78
Define Artificial Satellites
78-82
Scientists have sent many objects into space Some of these objects revolve round the Earth These are called artificial satellites.
Question: 79
Give the orbital speed formula for Artificial Satellite
79-82
The equation of orbital speed of a sate lite is
F=mv/r
According the this equation the satellite depends on gravitational acceleration of earth, velocity and radius of earth

Question: 80
On which factors gravitational acceleration depends
80-82
We know that According to formula gravitational acceleration depends upon height
Question: 81
With what force an apple weighing attracts the earth