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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 ### 0

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##### Question: 1
What is meant by the force of gravitation?
1-82
The force with which everybody in the universe attract another body towards itself is called gravitational force.
##### Question: 2
With what force an apple weighing 1 N attract the Earth?
2-82
According to Newton's law of gravitation apple attract the Earth with a force of 1 N.
##### Question: 3
Define orbital velocity.
3-82
The velocity of the satellite in its orbit is called orbital velocity.
##### Question: 4
What is meant by the force of gravitation
4-82
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: 5
What is gravitational field?
5-82
"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: 6
Why law of gravitation is important to us
6-82
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: 7
Do you attract the Earth or the Earth attracts you
7-82
We and earth both attract each other. Since the mass of Earth is very large, it attracts nearby objects with a significant force
##### Question: 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
How Newton's law of gravitation helps in understanding the motion of satellites
9-82
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: 10
Does an apple attract the Earth towards it?
10-82
Yes, according to law of law of gravitation, apple attracts the earth.
##### Question: 11
Explain the law of gravitation.
11-82
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: 12
Why we can not feel gravitational force around us
12-82
Due to small value of the gravitational force of attraction between object around us is very small and we do not feel it.
##### Question: 13
What is meant by GPS
13-82
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: 14
What is a field force?
14-82
Field force; Such a force which act on a body by another body without any physical contact is called field force.
##### Question: 15
What is consistence of gravitational law with Newton's third Law
15-82
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: 16
What is Satellite?
16-82
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: 17
On what factors the orbits speed of a satellite depends
17-82
Orbital speed of satellite depends upon following factors.
Height from earth surface
Gravitational aceleration
##### 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
Why earlier scientists could not guess about the gravitational force
19-82
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: 20
What are artificial satellites?
20-82
Scientist have sent many objects into space, Some of these objects revolved around the earth. These are called artificial satellites.
##### Question: 21
Write equation to determine mass of earth
21-82
Mass of earth can be determine by formula
M=R/g
and its value is M=6*10 kg
##### Question: 22
What is meant by geostationary orbit
22-82
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: 23
How can you say that gravitational force is a field force
23-82
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: 24
What is meant by gravitational field strength?
24-82
In the gravitational field of the earth, the gravitational force per unit mass is called the gravitational field strength of the earth.
##### Question: 25
Define orbital velocity
25-82
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: 26
What is the height and speed of Geo stationary satellite from the surface of the earth
26-82
The height of a geostationary satellite is about 42300km from the surface of the Earth Its velocity with respect to Earth is zero
##### Question: 27
Define force of gravitation.
27-82
Force of gravitation: The force due to which every body of the universe attracts every other body is called force of gravitation
##### 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
Why communication satellites are geostationary satellite?
29-82
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: 30
Explain the law of gravitation
30-82
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: 31
What is GPS?
31-82
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: 32
Why don't we feel the force of gravitation between objects around us in daily life
32-82
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: 33
Why is the value of g different at different place
33-82
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: 34
Does an apple attract the Earth toward it
34-82
yes, according to law of gravitation apple attracts the earth
##### 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
Give the orbital speed formula for Artificial Satellite
36-82
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: 37
Everybody has weight in Earth gravitational field
37-82
Weight of a body in Earth gravitational field is due to the gravitational force between the body and the Earth
##### Question: 38
What is the relation between the value of g and radius of Earth
38-82
As we know that: G=gm/r
##### Question: 39
What are artificial satellites
39-82
Scientist have sent many objects into space. Some of these objects revolved around the earth These are called artificial satellites.

##### Question: 40
What is meant by force of gravitation?
40-82
The force due to which everybodyof the universe attracts every other body is called force of gravitation
##### Question: 41
Can you determine the mass of our Moon
41-82
Yes We can determine the mass of our Moon by Newton's law of gravitation
##### Question: 42
Define Geostationary orbit
42-82
Geostationary orbit: An orbit in which Geostationary satellites travel is called Geostationary orbit
##### Question: 43
What do you known about G
43-82
G is a constant It called gravitational constant Its value is same every where.
##### Question: 44
On which factors gravitational acceleration depends
44-82
We know that According to formula gravitational acceleration depends upon height
##### Question: 45
What is the numerical values of g at Sun and Mars
45-82
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: 46
Define gravitational field
46-82
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: 47
Why communication satellites are stationed at geostationary orbits
47-82
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: 48
Define geo stationery satellite
48-82
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: 49
What is field force
49-82
The gravitational force acting on a object in gravitational field is called field force.
##### Question: 50
Define artificialsatellite?
50-82
Man made objects moving in fixed circular orbits around the Earth .
##### Question: 51
Why communication satellites appear stationary with respect to Earth
51-82
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: 52
What is a satellite
52-82
Satellite: An object that revolves around a planted is called a satellite

##### Question: 53
The weight of an object is less a=on moutains as compared on sesa level
53-82
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: 54
Explain how the value of g varies with altitude
54-82
The value of g at height (h) from the earth surface is given by
G=G/M/(r+h)
##### Question: 55
Give value and unit of G in gravitational law
55-82
Value of G in gravitational law is 6.673*10
##### Question: 56
With what force an apple weighting 1 N attracts the Earth.
56-82
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: 57
Define Natural satellite?
57-82
The moon revolves around the Earth as moon a natural satellite
##### Question: 58
With what force an apple weighing attracts the earth
58-82
According to Newton third law To every action there is a reaction Therefore the apple attracts the Earth with a force equal to its weight
##### Question: 59
Does the weight of an apple increases decreases or remain constant when taken to the top of a mountain
59-82
When an apple is taken to the top of mountain its weight decreases because the value of g decreases on mountains
##### Question: 60
Who is the first man who gave the idea of gravity?
60-82
The first man who came up with the idea of gravity was is99c newton.
##### Question: 61
How much Moon is away from the Earth and Completes its cycle around the Earth
61-82
Moon in nearly 3,80000 km away from the Earth it completes its one revolution around the Earth in 27.3 days
##### Question: 62
Define mass of earth
62-82
The quantity of matter in Earth is called Mass of Earth Its value is
##### Question: 63
How Newton's law of gravitation helps in understanding the motion of satellites?
63-82
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: 64
Write the values of Following
64-82
Radius of Earth Gravitational constant g Radius of Earth The value of Radius of Earth R is 6.4*10m
##### Question: 65
Do you attract the Earth or earth attracts you?
65-82
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: 66
What is meant by global positioning system
66-82
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: 67
What is the direction of gravitational field
67-82
The direction of gravitational field around the earth is always toward the centre of earth
##### Question: 68
On which factors the value of g on any celestial object depends upon
68-82
Value of g on the surface of a celestial object depends on its mass and its radius
##### Question: 69
What is the meant by communication satellite
69-82
Communication satellite: Satellites which was for commination are called communication satellites these are 423,00km away from surface of earth
##### Question: 70
State the difference between natural and artificial satellites.
70-82
Artificial Satellites: Scientists have sent many objects into space Some of these objects revolve around the Earth These are called artificial satellites.
##### Question: 71
What is difference between g and G
71-82
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: 72
Write the value and unit of gravitational constant G in SI units
72-82
Value In SI unit the value of G is
Unit: Nm kg
##### Question: 73
Why earlier scientists could not guess about the gravitational force?
73-82
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: 74
Define orbital velocity and write its formula
74-82
Orbital Velocity: The Velocity at which a body revolves about another body

##### Question: 75
What is meant by satellite
75-82
Satellites An object that revolves around a planet is called statellite
##### Question: 76
Why does the vale of g vary from place to place
76-82
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: 77
Define field force and gravitational field strength
77-82
Force Field: A force which is affect by a body due to any field is called force field
##### Question: 78
What is orbital speed of a low orbit satellite
78-82
A satellite revolving around very close to the Earth, has speed V nearly 8kms
##### Question: 79
With what force an apple weighing 1 N attract the Earth
79-82
According to Newton law of gravitation apple attract the Earth with a force of 1N
##### Question: 80
Can you determine the mass of our moon? If yes, then what do you need to know?
80-82
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: 81
How can you say that gravitational force is a field force