10 : GRAVITATION

Class 9 Science Examplar Chapter 10 : GRAVITATION

10. GRAVITATION

Class 9 Science Examplar Chapter 10 : GRAVITATION Choose the correct answers :

Q1. The SI unit of G (universal gravitation constant) is :

(A)

(B)

(C)

(D)

Ans : (D)

Q2. Mass of an object is 10 Kg , then its weight on the earth is :

(A) 98 N

(B) 89 N

(D) 96 N

Ans : (A) 98 N

[We have, N ]

Q3. How does the force of gravitation between two objects change when the distance between them is reduced to half ?

(A) The force of gravitation becomes 4 times more .

(B) The force of gravitation becomes 2 times more .

(D) The force of gravitation becomes time more .

Ans : (A) The force of gravitation becomes 4 times more .

Q4. The device used to measure the purity of milk is :

(A) Maltometer

(B) Hydrometer

(D) Hygrometer

Ans : (C) Lactometer .

Q5. The distance between two bodies becomes 8 times more than the usual distance , then the F becomes :

(A) 8 times

(B) 64 times

(D) times

Ans : (D) times .

Q6. The mass of body on moon is 60 kg , then the weight on the earth is :

(A) 240 N

(B) 360 N

(D) 320 N

Ans : (B) 360 N

[ The weight on the earth = 6 × 60 = 360 N ]

Q7. Two objects of different masses falling freely near the surface of moon would :

(A) have same velocities at any instant

(B) have different accelerations

(D) undergo a change in their inertia

Ans : (A) have same velocities at any instant .

Q8. The value of acceleration due to gravity

(A) is same on equator and poles

(B) is least on poles

(D) increases from pole to equator .

Ans : (C) is least on equator .

Q9. The gravitational force between two objects is F . If masses of both objects are halved without changing distance between them , then the gravitational force would become :

(A)

(B)

(D) 2F

Ans : (A) .

Q10. A boy is whirling a store tied with a string in an horizontal circular path . If the string breaks, the store :

(A) will continue to move in the circular path .

(B) will move along a straight line towards the centre of the circular path

(D) will move along a straight line perpendicular to the circular path away from the boy .

Ans : (C) will move along a straight line tangential to the circular path .

Q11. An object is put one by one in three liquids having different densities . The object floats with and parts of their volumes outside the liquid surface in liquids of densities and respectively . Which of the

following statement is correct ?

(A)

(B)

(C)

(D)

Ans : (D) .

Q12. In the relation , the quantity G :

(A) depends on the value of at the place of observation .

(B) is used only when the earth is one of the two masses

(D) is universal constant of nature

Ans : (D) is universal constant of nature .

Q13. Law of gravitation gives the gravitational force between :

(A) the earth and a point mass only

(B) the earth and sun only

(D) two charged bodies only

Ans : (C) any two bodies having some mass .

Q14. The value of quantity G in the law of gravitation :

(A) depends on mass of earth only

(B) depends on radius of earth only

(D) is independent of mass and radius of the earth .

Ans : (D) is independent of mass and radius of the earth .

Q14. Two particles are placed at some distance . If the mass of each of the two particles is doubled , keeping the distance between them unchanged,the value of gravitational force between them will be –

(A) times

(B) 4 times

(D) unchanged

Ans : (B) 4 times .

Q15. The atmosphere is held to the earth by :

(A) gravity

(B) wind

(D) earth’s magnetic field

Ans : (A) gravity .

Q16. The force of attraction between two unit point masses separated by a unit distance is called :

(A) gravitational potential

(B) acceleration due to gravity

(D) universal gravitational constant

And : (D) universal gravitational constant .

Q17. The weight of an object at the centre of the earth of radius R is :

(A) zero

(B) infinite

(D) times the weight at surface of the earth

Ans : (A) zero

Q18. An object weight 10N in air . When immersed fully in water, it weighs only 8N .The weight of the liquid displaced by the object will be

(A) 2 N

(B) 8 N

(D) 12 N

Ans : (A) 2 N .

Q19. A girl stands on a box having 60 cm length , 40 cm breadth and 20 cm width in three ways . In which of the following cases , pressure exerted by the brick will be :

(A) maximum when length and breadth form the base

(B) maximum when breadth and width form the base

(D) the same in all the above three cases .

Ans : (B) maximum when breadth and width form the base .

Q20. An apple falls from a tree because of gravitational attraction between the earth and apple . If is the magnitude of force exerted by the earth on the apple and is the magnitude of force exerted by the apple on earth , then –

(A) is very much greater than

(B) is very much greater than

(D) and are equal .

Ans : (D) and are equal .

Q21. A ball is thrown up, the value of g will be :

(A) negligible

(B) negative

(D) zero

Ans : (B) negative .

Q22. The accepted value of G is :

(A)

(B)

(C)

(D)

Ans : (A)

Class 9 Science Examplar Chapter 10 : GRAVITATION Fill in the blanks :

23. is a weak force unless large masses are involved .

Ans : Gravitation .

Q24. Force of gravitation due to the earth is called .

Ans : gravity .

Q25. Relative density .

Ans : Density of water .

Q26. The of an object is constant and does not change from place to place .

Ans : mass .

Q27. The of an object is the force with which it is attracted towards the earth .

Ans : weight .

Q28. The is equal to the product of mass and acceleration due to gravity .

Ans : weight .