Matric Part 1/9th Class Physics Chapter 5 Long Question With Answer for Unit 5 Gravitation

Question # 1

How gravitation is discovered. what is the force of gravitation

Ans 1: The first man who came up with the idea of gravity was Isaac newton. It was an evening of 1665 when he was trying to solve the mystery why planets revolve around the sun. Suddenly an apple fell from the tree under which he was sitting. The idea of gravity flashed in his mind. he discovered not only the cause of falling apple but also the cause that makes the planet to revolve around the sun and the moon around the earth.
Force of gravitation: force due to which every body of the universe attracts every other body is called force of gravitation.

Question # 2

State and explain Newtons law of gravitation. Also derive its equation

Ans 1: Law of gravitation: Every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
Ans 2: Note; we don not feel the gravitational force between different objects around us because it is very small. However we can observe the effect of gravitational force easily, if the mass of one or both objects is very large . Since the mass of earth is very large, it attracts nearby objects with a significant force. The weight of an object on the earth is a result of the gravitational fore between the two masses.

Question # 3

Q no: (B) A polar satellite is launched at 850 km above earth. Find its orbital speed.

Ans 1: Solution:
Height= 850 km
= 850 x 1000m
850000m = 8.5 x 10⁵m
orbital speed = v=?
V=√GMe/(R+h)
=√6.673 x 10-¹¹ x 6 x 10²⁴/(6.4 x 10⁶ + 8.5 x 10⁵ )
= 743.13 ms-¹

Question # 4

How will you relate law of gravitation and Newtons third law of motion

Ans 1: in law of gravitation it is to be noted that mass m1 attracts m2 towards it with a force F while mass m2 attract m1 towards it with a force of the same magnitude F but in opposite direction. If the force acting on m1 is considered as action then the force acting on m2 will be the reaction . We can say that the action and reaction due to force of gravitation are equal in magnitude but opposite in direction. This is in consistent with newtons third law of motion which states , to every action there is always an equal but opposite reaction

Question # 5

Q no: (B) A polar satellite is launched at 850 km above earth. Find its orbital speed.

Ans 1: Solution:
Height= 850 km
= 850 x 1000m
850000m = 8.5 x 10⁵m
orbital speed = v=?
V=√GMe/(R+h)
=√6.673 x 10-¹¹ x 6 x 10²⁴/(6.4 x 10⁶ + 8.5 x 10⁵ )
= 743.13 ms-¹

Question # 6

Q no: 6 (A) State Law of gravitation and derived the equation.

Ans 1: Everybody 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 centres.
F x m1m2
F x 1/d²
F x m1m2/d²
F= Gm1m2/d²

Question # 7

Describe the motion of artificial satellite and derive the formula for the orbital speed of the artificial satellite

Ans 1: Artificial satellite: Artificial satellites are launched for space research and telecommunication. With their help, we are able to enjoy live coverage of cricket matches, Olympic games and many other programs directly on our television sets.
Artificial satellites keep on revolving around the earth in different geo stationary satellite orbits with uniform speed due to gravitational force

Question # 8

State and explain gravitational field

Ans 1: Gravitational pull of earth acting on the body whether the body is in contact with earth or not is called the field force and the are for this force around the earth is called gravitational field
Ans 2: For example: the velocity of a body, thrown up, goes on decreasing while on return its velocity goes on increasing. It is due to the gravitational pull earth acting on the body, which is a field force. It is assumed that a gravitational field exists all around the earth. This field is directed towards the center of the earth. The gravitational field becomes weaker and weaker as we go farther and farther away from the earth
Ans 3: Gravitational field strength: in the gravitational field 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

Question # 9

Q no 7 (A) Explain the motion of Artificial satellites.

Ans 1: A satellite requires centripetal force of attraction between the salellite and the Earth provides the necessary centripetal force.
Consider a satellite of mass revolving round the earth at an altitude h in a orbit of radian to with orbital velocity Vo The necessary centripetal force required is given by equation
fc = mv²o/r_o
Fc = w^' = mg_n
mg_hmv²o/r_o
V_o²= g_h ro
vo= √g_hro
V_o= √g_n(R+h)
Equation ( 5.10) gives the velocity which a satellite must possess when launched in an orbit of radius r_o=9R+h) around the Earth
R+h= R
g_n = g
v_o=√gR
A satellite revolving around very close to the Earth has speed V_o nearly 8kms-¹ or 29000 kmh-¹

Question # 10

Q no: 6 (B) Calculate the value of g at a height of 3600 km above the surface of the Earth.

Ans 1: Solution:
g_n =?
h = 3600km = 3600 x 1000m
R = 6400 x 10³ m
G = 6.673 x 10-¹¹ Nm²kg-²
Me = 6x 10²⁴ kg
g = GMe/R²
g_n = Gme/(R+h)²
6.673 x10-¹¹ x 6 x 10²⁴/6400 x10³ + 3600 x10³
g_n = 4ms-²

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Matric Part 1/9th Class Physics Chapter 5 Long Question With Answer for Unit 5 Gravitation

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Online Long Questions For Chapter 5 "9th Class Physics Chapter 5 Long Question Preparation "

Physics (New Book) - 9th Class Physics Chapter 5 Long Question Preparation

How gravitation is discovered. what is the force of gravitation

State and explain Newtons law of gravitation. Also derive its equation

Q no: (B) A polar satellite is launched at 850 km above earth. Find its orbital speed.

How will you relate law of gravitation and Newtons third law of motion

Q no: (B) A polar satellite is launched at 850 km above earth. Find its orbital speed.

Q no: 6 (A) State Law of gravitation and derived the equation.

Describe the motion of artificial satellite and derive the formula for the orbital speed of the artificial satellite

State and explain gravitational field

Q no 7 (A) Explain the motion of Artificial satellites.

Q no: 6 (B) Calculate the value of g at a height of 3600 km above the surface of the Earth.

Prepare Complete Set Wise Questions For Chapter 5 "9th Class Physics Chapter 5 Long Question Preparation "

Set 1

9th Class Physics Chapter 5 Long Question Preparation - Set 1

How gravitation is discovered. what is the force of gravitation

State and explain Newtons law of gravitation. Also derive its equation

Q no: (B) A polar satellite is launched at 850 km above earth. Find its orbital speed.

How will you relate law of gravitation and Newtons third law of motion

Q no: (B) A polar satellite is launched at 850 km above earth. Find its orbital speed.

Q no: 6 (A) State Law of gravitation and derived the equation.

Describe the motion of artificial satellite and derive the formula for the orbital speed of the artificial satellite

State and explain gravitational field

Q no 7 (A) Explain the motion of Artificial satellites.

Q no: 6 (B) Calculate the value of g at a height of 3600 km above the surface of the Earth.

9th class Physics Chapter 5 Long Q's (English Medium)

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