KSEEB Solutions For Class 9 Science Chapter 10 Gravitation

KSEEB Solutions For Class 9 Science Chapter 10 Gravitation Important Concepts

Gravitation: It is the force of attraction between any two bodies in the universe
Gravity: It is the force of attraction between a planet and an object on its surface
The universal law of gravitation: Every object in the universe attracts every other object with a force which proportional to the product of their masses and inversely proportional to the square of the distance between them.
Universal gravitational constant: It is the gravitational force between two objects of unit mass with unit separation. It’s value is 6.67 x 10^-11 Nm²/kg²Acceleration due to gravity: It is the acceleration of an object tailing towards the earth due to the earth’s gravity. It’s value on the surface is 9.8m/s²Free fall: The motion of an object under the influence of earthing’s gravity only is called tree fall
Mass: It is the quantity of matter contained in a body. It’s value does not change with places and its S. I unit is a kilogram (kg)
Weight: It is the force with which a body is attracted by the earth and it’s value varies from place to place. Its S.I. unit is newton (N). Weight is given by W = mg
Density: It is the ratio of mass by the volume of a substance is density^ mass/volume and the S.I unit is kg/m³

KSEEB Solutions for Class 9 Science Chapter 10

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Class 9 Social Science

Class 9 Science

Class 9 Maths

Relation between g and G: g = GM/R²where g – acceleration due to gravity, G = universal gravitational constant, M = mass of the earth and R = mean radius of the earth
Equations of objects under Earth’s gravity:
(1) v = u + gt
(2) s = ut + ½ gt²(3) v² = u² + 2gs
Fluid: A substance that can flow is called a fluid. Example: gases and liquids.
Thrust and Pressure: The force acting on an object perpendicular to the surface is called thrust and the thrust per unit area is called pressure. S.I unit pressure is N/m²= pascal
Buoyancy: When an object is immersed in a liquid, then the upward force exerted by a liquid on the object is called upthrust or buoyancy. The magnitude of buoyancy depends on the density of the liquid
Archimedes’s Principle: When a body is immersed completely or partially in a fluid, it experiences an upward force that is equal the weight of the fluid displaced by the body.
Relative density: Relative density of a substance is defined as the ratio of the density of the substance to the density of water. It has no unit.

KSEEB Solutions For Class 9 Science Chapter 10 Gravitation

Gravitation Exercises

Question 1. State universal law of gravitation
Answer: Every object in the universe attracts every other object with a force which proportional to the product of their masses and inversely proportional to the square of the distance between them.

Question 2. Write the formula to find the magnitude of the gravitational force between the earth and an object.
Answer: F = G Mm/R²

KSEEB Class 9 Science Chapter 10 Gravitation Solutions

Question 3. What do you mean by free fall?
Answer: The motion of a body under the influence of the earth’s gravity

Question 4. What do you mean by the acceleration due to gravity?
Answer: It is the acceleration of an object falling to ward’s earth’s center due to the earth’s gravity

Question 5. What are the differences between the mass of an object and its weight
Answer:
Mass:

It is the quantity of matter contained in a body
Its value does not change
It is a scalar quantity
It is expressed in kg
It can never be zero

Weight:

It is the force with which a body is attracted toward the center of the earth
Its value changes from place to place
It is a vector quantity
It is expressed in newton
It is zero at the center of the earth

Question 6. Why is the weight of an object on the moon is 1 /6th its weight on the earth?
Answer: This is because the gravitational attraction on the moon is 1/6 th of that on the earth.

Question 7. Why is it difficult to hold a school bag with a thin and strong string?
Answer: Thinner the string, the smaller is the area of the cross-section, and the greater will be the pressure.

Question 8. Why does an object float or sink when placed on the surface of the water?
Answer: A cork placed on water floats while the nail sinks because of their difference in their densities. The density of the cork is less than the density of water. This means that the upthrust of water on he cork is greater than the weight of the cork. So it floats. The density of iron nail is more than that of water. This means that the upthrust by water on he iron nail is less than the weight of the nail. Hence the nail sinks.

Question 9. You find your mass to be 42kg on a weighing machine. Is your mass more or less than 42kg?
Answer: Slightly more than 42 kg. The upward thrust of air acts on our body which reduces our original mass.

Question 10. You have a bag of cotton and an iron bar, each indicating a mass of 100kg when measured on a weighing machine. In reality, one is heavier than the other. Can you say which one is heavier and why?
Answer: The bag of cotton is heavier because the cotton bag has a larger area and it experiences a larger upthrust of air than the iron bar. This means that the weighing machine shows a smaller mass for the cotton bag than the original mass which is more ‘ than 100kg.

Gravitation Textual Questions

Question 1. How does the force of gravitation between two objects change when the distance between them is reduced to half?
Answer: Since F∞1/r², when the distance is reduced to r/2, then the new force ∞ 4/r^2. The fore becomes 4 times the initial force

Question 2. Gravitational force acts on all objects in proportion to their masses. Why then a heavy object does not fall faster than a light object?
Answer: Although F cc m, g is independent of the mass of the body. Hence all the bodies reach the ground at the same time in absence of air resistance.

Question 3. What is the magnitude of the gravitational force between the earth and a 1 kg object on its surface ( Mass of earth = 6 x 1024 kg and R = 6.4 x 106 m)
Answer:
F = G Mm/R²

\(=\frac{6.67 \times 10^{-11} \times 6 \times 10^{24} \times 1}{\left(6.4 \times 10^6\right)^2}=9.8 \mathrm{~N}\)

Question 4. The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth Why?
Answer: Both the earth and moon attract each other with the same force. This is because neither the earth nor the moon is toward each other.

Question 5. If the moon attracts the earth, why does the earth not move toward the moon?
Answer: Based on Newton’s 3rd law of motion, the earth also attracts the moon with equal and opposite force.

Karnataka Board Class 9 Science Chapter 10 PDF

Question 6. What happens to the force between two objects, if
(1)The mass of one object is doubled?
(2)The distance between the objects is doubled and trebled?
(3)masses of both objects are doubled
Answer:
(1) Since force is directly proportional to mass, force is doubled
(2) Since the force(F) is inversely proportional to the square of the distance between the objects, he force becomes F/4 when the distance is doubled and F/9 when the force is trebled
(3) Since the force is proportional to the product of masses, the new force will be 4F

Question 7. What is the importance of the universal law of gravitation?
Answer: The universal law of gravitation explains
1) The force that binds us to earth
2) The motion of the moon around he earth
3) The motion of the planets around the sun
4) The tides in sea and ocean

Question 8. What is the acceleration of free fall?
Answer: It is the acceleration produced on a body due to
the earth’s gravity.

Question 9. What do we call the gravitational force between the earth and an object?
Answer: Weight of the object

Question 10. Amit buys few grams of gold at poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why?
Answer: No. Due to the change in the value of g, the weight of a body is always less than its weight at the equator. Hence the gold weight will be less then its weight at the equator.

Question 11. Why will a sheet of paper fall slower than one that is crumpled into a ball?
Answer: Due larger surface area, the paper sheet experiences more air resistance and hence it falls slowly.

Question 12. The gravitational force on he surface of the moon is only 1/6 th of the earth. What is the weight in new tons of a 10kg object on the moon and on the earth?
Answer:

On the earth, the weight of the object=10 g= 10x 9.8 = 98N
On the moon, weight of the object = 10 x g/6 = 10 x 9.8/6 = 16.3N

Question 13. A ball is thrown vertically upwards with a velocity of 49m/s. Calculate
(1)The maximum height to which it risees?
(2)The total tiem it takes to return to the surface of the earth?
Answer:
(1) Here u = 45m/s and g = – 9.8 m/s². At the maximum height v = 0

Using the equation v² – u² = 2gs,

we get 0² – (45)² = 2 (-9.8) s => s – 122.5m

Thus maximum height the ball rises is 122.5m

(2) Again using the equation v=u + at, we get 0 = 45 – 9.8 t => t = 5s

Since time to reach maximum height = time to reach the ground from a maximum height

Total time is taken by the ball to return to the earth’s surface = 5 + 5 = 10s

Class 9 Science Chapter 10 KSEEB Important Questions

Question 14. A stone is released from he top of a tower of height 19.6m. Calculate its final velocity just before touching the ground
Answer: Given u = 0, g = 9.8m/s2,s= 19.6m, v = ?

Using the equation

v² – u² = 2gs => v²– 0 = 2(9.8) (19.6) = (19.6)²(why?)

Hence \(v=\sqrt{(19.6)^2}=19.6 \mathrm{~m} / \mathrm{s}\)

KSEEB Solutions For Gravitation Short Notes

Question 15. A stone is thrown vertically upward with an initial velocity of 40m/s. Taking g = 10m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?

Answer: We have u = 40m/s, g = – 10m/s²and at the maximum height v = 0

Using the equation v²-u² = 2gs , we get v²– (40)²

= 2(- 10) s => – 20s = – 1600 => s = 80m

The total distance covered by the stone = 80 + 80= 160m

Net dispalcement = 0

Question 16. Calculate the force of gravitation between the earth and the sun given that the mass of the earth is 6 x 1024 kg and of the sun is 2 x 1(Pkg. The average distance between the two is 1.5 x 10n m
Answer:
F =\(\mathrm{G} \frac{M_E M_S}{r^2}\)

\(=6.67 10^{-11} \times 6 \times 10^{24} \times 2\times 10^{30} /\left(1.5 \times 10^{11}\right)^2\)

On simplification, we get F = 3.56 x 10²² N

Question 17. A stone is allowed to fall from the top of a tower 100m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25m/s. Calculate when and where the stones meet.
Answer:
Let the stones meet at a height x from the ground after time ‘t’ second

For the falling stone, u = 0, g = l0 m/s² g = 100 -x

Using the equation s = u t + 1/2 gt², we get

100- X = (0) t + 1/2 (10) t² …………….. (1)

For the upward stone,

u = 25m/s, g = -10m/s2 s = x

Hence x = 25t – 1/2(10) t² …………….(2)

Adding equations (1) and (2), we get 100 = 25t => t = 100/25 = 4 sec

The two stones meet each other after 4 second

When t = 4, x = 25 (4) – 1/2 (10) (4)² x =

100-80-20m

I.e, The stones meet at a height 20m from the ground.

Question 18. A ball thrown up vertically returns to the thrower after 6 sec. Find
1) Velocity with which it was thrown up?
2) The maximum height it reaches, and
3) The position after 4 second
Answer:
Time to reach maximum height = 6/2=3 second

1) Now, t = 3s, v = 0, g = – 9.8 m/s² and u =?

v = u + gt 0 = u — 9.8 (3) u => 29.4m/s

2) S _max= ut + 1/2 gt² = 29.4 (3) – 1/2(9.8) (3)²

= 44.1 m

3) S _{(t = 4)}= 29.4 (4) – 1/2 (9.8) (3)²= 39.2m from the ground

Question 19. In what direction does the buoyant force on an object immersed in a liquid act?
Answer: In the vertical direction through the center of gravity.

Question 20. Why does a block of plastic released under water come up to the surface of the water?
Answer: It is due to the upthrust exerted by the water the block of plastic.

Question 21. The volume of a substance is 20 cm-1. If the density of water is 1 g/cm3, will the substance float or sink?
Answer: Density of substance = 50/20 = 2.5g.cm3 > the density of water. Hence the substance will sink into the water.

Question 22. The volume of a 500g sealed packet is 350 cm3. Will the packet float or sink in water if the density of water is 1g/cm³? What will be the mass of the water displaced?
Answer:
Density of packet = 500/350 = 1.43g/cm³ > density of water (1.2g/cm³).
Hence the packet will sink.

The volume of water displaced = volume of the sealed packet = 350cm³

Therefore, a mass of water displace = 350 x 1 = 350g

KSEEB Class 9 Science Chapter 10 Important Questions

Gravitation Additional Questions

Question 1. What is the S.I. unit of universal gravitational constant
Answer: Nm² kg ^-2

Question 2. What is the accepted value of the universal gravitational constant?
Answer: 6.673 x 10^-4 Nm²kg^-2

Question 3. What is free fall?
Answer: When an object falls under the earth’s gravitational force above, then the object is said to be in free fall

Question 4. The mass of an object is 19kg. What is its weight on the earth?
Answer:
Weight of the object (w) = mg

= 10 x 9.8 = 98 N

Question 5. What is weightlessness?
Answer: A body is said to be in a state of weightlessness when the reactionary force of the supporting surface is zero.

Question 6. One kg – wt is equal to how many Newton’s?
Answer:
1 kg wt = 1kg x 9.8ms^-2 = 9.8 N

Question 7. State two factors on which the gravitational force between two objects depends
Answer:
1) Masses of the objects
2) Distance between the objects

Question 8. Who formulated the universal law of gravitational
Answer: Issac Newton

Question 9. What is the value of the universal gravitational constant
Answer: G =6.67 x 10^-11 Nm²kg^-2

KSEEB 9th Science Chapter 10 Gravitation Exercise Answers

Question 10. On what factors weight of a body depend?
Answer: Mass and acceleration due to gravity

Question 11. Why does a man feel lighter on the moon?
Answer: On the moon, the gravity is less than that of the earth.

Question 12. What is weightlessness?
Answer: When the surface offers zero reactionary force on a body kept on it is said to be weightless.

Question 13. The value of g is not same at all places on the earth. Why?
Answer: This is due to the shape of the earth and its rotation about its own axis

Question 14. Is weight a scalar or a vector?
Answer: Weight is a vector quantity

Question 15. How many newtons are equal to one kg – wt?
Answer: 9.8N

Question 16. What is the value of g at the center of the earth?
Answer: zero

Question 17. What is the mass of an object whose weight is 19.6N
Answer: m = W/g = 19.6/9.8 = 2kg

Question 18. An astronaut feels weightlessness in space graft?
Answer: It is because no gravitational force acts on the astronaut

Question 19. What happens to the mass and weight of a stone broght fron the moon to the earth?
Answer: Mass remains the same while the weight increases

Question 20. What is fluid?
Answer: A substance that can flow is called a fluid.

Two Marks Questions

Question 21. How does gravitation differ from gravity?
Answer: Gravitation refers the force of attraction between any two bodies in the universe whereas gravity refers the force of attraction between the earth and any object on its surface.

Question 22. What do you understand by buoyancy?
Answer: The phenomenon of an upward force acting on a body partially or completely immersed in a fluid is called buoyancy

Question 23. What is the value of
1) On the surface of the earth
2) At the center of the earth
Answer:
1) on the surface g = 9.8ms’2
2) At the center, g = 0.

Karnataka Board 9th Science Chapter 10 Laws of Gravitation

Question 24. How does the value of g vary with
1) altitude
2) latitude
Answer:
1) g decreases with an increase in altitude
2) g is m make at poles and minimum at the equator.

Question 25. Mean’s weight on the surface of the earth is SOON. What will be her weight at the height 2R (where R = Radius of the earth)
Answer:
Weight on the earth W = \(G \frac{M m}{R^2}\)

Weight on the height 2R =\(\mathrm{W}^i \)=\( G \frac{G M m}{(2 R)^2}\)

\(\frac{W^1}{W}=\left(\frac{G M m}{4 R^2}\right) / \frac{G M m}{R^2}=1 / 4\) \(W^1=\frac{1}{4} \times W=1 / 4 \times 500=125 N\)

Question 26. You feel less weigher in water than outside the water. Why?
Answer: Because inside the water, the body experiences an upthrust by water.

Question 27. State Archimedes’ principle
Answer: When a body is immersed fully or partially in a fluid it experiences an upward thrust equal to the weight of the fluid displaced by it

Question 28. Name any devices that work on Archimedes’s principle
Answer:
1) Lactometer – used to measure the purity of milk
2) Hydrometer – used to measure the density of liquids

Question 29. Define the relative density of a substance
Answer: It is the ratio of the density of the substance to the density of water at 4°C

Question 30. On what factors the buoyant force depends on?
Answer:
1) Density of the liquid
2) The volume of the body immersed in the liquid

Question 31. Why does an army tank rest upon a continuous heavy chain?
Answer: Due to the larger area of the chain, the pressure exerted by the tank will be less and this prevents the sinking of the ground.

Question 32. A sharp knife cut better than a blunt one. Why?
Answer: Sharper the edge, the lesser will be the area of the edge. Hence effective force per unit area ie pressure is more.

Question 33. State the conditions for
(1) floatation of a body on a liquid
(2) sinking of a body in a liquid
Answer:
(1) A body will float if its density is less than the density of the liquid
(2) The body will sink if the density of the body is greater than the density of the liquid.

Question 34. When a fresh egg is placed in water it sinks. On dissolving a large amount of salt in the water, the g begins to rise and float. Why?
Answer: The density of the fresh egg is more than that of water. Hence it sinks. When salt is added to water, the density of water becomes more than that of egg. Hence the egg begins to float on water.

Question 35. The weight of an object on the earth is 12N. What would be its weight on the moon?
Answer:
We Know That

Weight on the moon =1/6 x weight on the earth

= (1/6) x 12

= 2N

Three Marks Questions

Question 36. Give reasons for the following:
(1)Pins and nails have pointed ends
(2) Building has wide foundation
(3)A camel walks easily on the sand but a man cannot
Answer:
(1) The pointed ends have very small area and hence the force per unit area ie pressure will be greater on the surface which makes them to penetrate the surface
(2)Due to larger surface area of the larger foundation, the effective force/area of the building on the ground will be less. This prevents the sinking of the ground.
(3)Feet of the camel are larger than that of man. Hence camels experience lower pressure than the man. This makes camel to walk easily on the sand.

Question 37. The mass of the earth and the moon are 6 x 10²⁴ kg and 7.4 x 10²² kg respectively. The distance between the earth and the moon is 3.84 x 104 km. Calculate the force exerted by the earth on the moon. G= 6.7 x 10 ^-11 Nm²kg^-2.
Answer: Mass of the earth (M) = 6 x 10²⁴kg, Mass of the moon (m) = 7. 4 x 10²² kg, and distance between the earth and the moon (d) = 3.84 x 10⁵km = 3.84 x 10⁸ m

According to Newton’s universal law of gravitation, the force between the earth and the moon is

F = G Mm/d² = \( \frac{6.7 \times 10^{-11} \times 6 \times 10^{28} \times 7.4 \times 10^{22}}{\left(3.84 \times 10^8\right)^2}\)

\(=2.0110^{20} \mathrm{~N}\)

Question 38. Derive an expression for acceleration due to gravity acting on an object on the surface of the earth.
Answer: According to Newton’s second law of motion, Force acting on an object of mass (m) and tailing with acceleration (g) is given by F = mg …………………(1)

According to Newton’s universal gravitational law of gravitation, the force of attraction between the object and earth is given by F₈ = G Mm/R²…………………(2)

Comparing equations (1) and (2), F = F₈ mg = G Mm/R² => g = GM/R2

Question 39.
1) Define Thrust and pressure. Mention their S.I units
2) A block of wood is kept on a table top. The mass of the wooden block is 5 kg and its dimensions are 40cm x 20cm x 10cm. Find the pressure exerted by the wooden block on the table top if it is made to lie on the table top with its sides of dimensions (a) 20cm x 10cm and b) 40cm x 20cm
Answer:
1) Thrust: It is the force acting on an object perpendicular to the surface.

Pressure: It is thrust per unit area of contact ie P = F/A

S.I unit thrust is newton (N) and S.I unit of pressure = Nm²

2) Case (1) Thrust on the table (F) = mg – 5 x 9.8 = 49N

Area of the face on the table = 20 x 10 cm²

= 0.02m²

Hence pressure = F/A = 49/0.02 = 2450N/m²

Case (2) Area of the face on the table=40 x 20 cm²= 0.08 m²

Hence pressure = 49/0.08 = 612.5 N/m²

Four Marks Questions

Question 40. Give reasons:
1) You apply more pressure on loose sand when you stand than when you Me down
2) An iron nail floats on mercury but sinks in water
3) It is easier to swim in sea water than in river water
Answer: Pressure is inversely proportional to the area of contact. The area of contact is less when we stand on the loose sand. Hence we apply more pressure.

Question 43. State and explain the universal law of gravitation. Hence obtain the S.I. unit of the universal gravitational constant
Answer:
Statement: Every object in the universe attracts every other object with a force that is proportional to their masses and inversely proportional to the square of the distance between them. The force acts along the lining the centers of the objects.

Explanation:

Gravitational

consider two objects A and JB of masses M and M lie at a distance ’d’ from each other . Let F be the force of attraction between the two objects. According to the universal law of gravitation

1) \( F \propto \frac{M m}{q^2}\)

2) \( F \alpha \frac{\Phi}{d^2}\)

combining equations (1) and (2), we get

\(F \alpha \frac{M m}{d^2}\) or

\( F=G \frac{M m}{d^2}\)

where G is the constant of proportionality and is called the universal gravitation constant.

To find the S.T. unit of G

From Equation (3)

\(\mathrm{G}=\frac{F \times d^2}{M m}\)

substituting units of F, d, M ie N, m, and kg, we get

S.L unit of G= Nm² kg ²

Class 9 Science Chapter 10 Gravitation KSEEB Notes

Question 41.
1) state universal law of gravitation
2) Mention any four phenomena explained by the universal law of gravitation.
Answer:
1) Every object in the universe attracts every other object with a force that is proportional to their masses and inversely proportional to the square of the distance between them.
2) Universal law of gravitation explained the following phenomenon.

The force that binds us to the earth
The motion of the moon around the earth
The motion of the planets around the sun
The tides due to the moon and the sun.

Question 42. using the following data, prove that weight of the object on the moon = (1/6)th of its weight on the earth

celestial body Mass (kg) Radi (in)

Earth 5.98 x10²⁴ 6.37 x10⁶

Moon 7.36 x10²²1.74 x106

Answer: According to the universal law of gravitation, the weight of an object on the moon is given by

\(W_m=G \frac{M_m m}{R_m^2}\) ………………………………(1)

where m = mass of the body the weight of the same object on the earth is given by

\( W_E=G \frac{M_e \times m}{R_e^2}\) …………………………..(2)

Dividing Eqn (1) by Eqn (2), we get

\( \frac{W_m}{W_e}=\frac{M_m}{M_e} \times \frac{R_e^2}{R_m^2}\) \(\frac{W_m}{W_e}=\frac{M_m}{M_e} \times \frac{R_e^2}{R_m^2} \frac{7.36 \times 10^{22}\left(6.37 \times 10^6\right)^2}{5.98 \times 10^{24} \times(1.74) \times 10^6}\) \( \frac{W_m}{W_e}=\frac{2.431 \times 1010}{1.474 \times 1011}=0.165=1 / 6\) \( W_m=\frac{1}{6} \times W_e\)

Thus, the weight of an object on the moon is (1/6)th of its weight on the earth

Question 43. Distinguish between Mass and Weight
Answer:
Mass

Mass is the quality of material present in a body
The value of mass remains the same at all places.
It is a scalar quantity
S.I. unit is kilogram
Measured by a pan balance
Mass can never be zero

Weight

It is the gravitational force exerted by the earth on the body.
The value of weight changes as the ‘g’ value changes from place to place
It is a vector quantity
S.I. unit is kilogram weight or newton
Measured by a spring balance
Weight is zero at the center of the earth.

Question 44.
1) Define acceleration due to the gravity of earth
2) On what factors acceleration due to gravity depends
3) Where is cg’ greater – at poles or equator
Answer:
1) The acceleration produced in the motion of a body under the gravitational force of the earth is called acceleration due to gravity.
2) Acceleration due to gravity depends on

The shape of the earth
Altitude from the surface of the earth.
Depth from the surface of the earth
Latitude of the place.

3) g is greater at poles

Question 45.
(1) What is gravity?
(2) Mention any three differences between g and G
Answer:
1) Gravity is the force of attraction between the earth and any object on the surface.
2) acceleration due to gravity (g)

It is acceleration acquired by a body by virtue of the earth’s gravity
It is equal to the force of attraction between two unit masses separated by unit distance
Its value depends on altitude, latitude shape of the earth, etc.,
S.I.unit is ms^-2

Universal gravitation constant IG)

It is equal to the force of attraction between two unit masses separated by unit distance
It is a quantity
It is a universal Constance
Nm²kg²

Gravitation Application Questions

Question 1. The weight of an object on the earth is I2N. What would be its weight on the moon?
Answer:
We Know That
Weight on the moon = 1/6 x weight on the earth

= 1/6 x12

= 2N

Question 2. A stone is brought from the moon to the earth? What happens to the mass and weight of the stone on the earth?
Answer: Mass remains the same Weight increases.

Question 3. What is the value of the universal gravitational constant of the center of the earth?
Answer: G = \(6.673 \times 10^{11} \mathrm{Nm}^2 \mathrm{~kg}^{-2}\)

Question 4. The moon attracts the earth. Why does the earth not move toward the moon?
Answer: acceleration \( \alpha \frac{1}{m a s s}\)

Since the mass of the earth is very large, the acceleration produced in the earth is negligible.

Karnataka Board Class 9 Physics Chapter 10 MCQs

Question 5. If the earth shrinks and mass remains the same, what happens to the weight of a person?
Answer:
We Know That

\(\mathrm{g}=\frac{G M}{R^2}\)

When the earth shrinks, R decreases. This leads to an increase in g and therefore weight = mg also increases.

Question 6. When a piece of paper and a stone are dropped from the top of a building, the paper takes longer time. Why?
Answer: Since the paper has more surface area it experiences more air friction than the stone.

Question 7. On the earth’s surface mass remain constant while weight changes from the equator to the pole Why?
Answer: Since ‘g’ varies from equator to pole weight = mg also varies.

Question 8. Mass of a planet is (1/3)rd of the earth its radius is half of the earth. What will be acceleration due to gravity
Answer:
M1 – Mass of the planet
R1 = Radius of the planet k-riME and Rl = VL RE

Question 9. Buying gold at the equator and selling the same at the poles is profitable. Why?
Answer: The weight of gold at the poles will be higher than its weight at the equator.