Gravitation Exercise # 1

EXERCISE # 1 Q.1 Give the formula to calculate the gravitational force of attraction. Q.2 What is the value of gravitational constant ? Q.3 What is the unit of gravitational constant ? Q.4 Does the gravitational force between two bodies change, if some other material body is placed between them ? Q.5 What is the approximate value of acceleration due to gravity on the surface of earth ? Q.6 What is the unit of acceleration due to gravity? Q.7 State the relation between g and G on earth. Q.8 What is the effect of altitude on the value of g ? Q.9 What is the weight of a body at a height equal to the radius of earth above the earth's surface ? Q.10 Is the weight of body more at the equator or at poles ? Q.16 How does the gravitational force change between two objects when the distance between them is doubled ? Q.17 Why two stones do not come closer, even if there is gravitational force of attraction between them ? Q.18 Under what conditions our weight becomes zero? Give examples. Q.19 An astronaut inside a spaceship orbiting round the earth feels weightlessness. Explain. Q.20 The weight of a body is less inside the earth than on the surface. Why? Q.21 For two bodies of different masses, acceleration due to gravity is same or different? Explain. Q.22 Newton's law of gravitation states that there is a force of attraction between two bodies. Why do we not observe the motion of two stones lying on the floor moving towards each other ? / Q.23 Calculate the force of attraction between two bodies of masses 100 kg and 60 kg respectively separated by a distance of 5 m from each other. Q.11 Which force is responsible for the earth revolving round the sun ? Q.12 A stone is released from some height, it moves towards the earth. Does the earth also move towards the stone ? Q.24 If the distance between two bodies is decreased by a factor of 4, by what factor the force of attraction will change ? Q.13 A light and a heavy body, both are dropped simultaneously from the same height. Which will strike the ground earlier ? Q.25 Q.14 As we go inside the earth, what is the effect on the value of g ? Calculate force of attraction on a body of mass 50 kg lying on the surface of earth. Given that the mass of earth = 6 × 1024 kg radius of the earth = 6.4 × 106 m and G = 6.67 × 10–11Nm2/kg2. Q.26 What happens to the weight of a body when it is falling freely under gravity ? Q.15 What is the value of g at the centre of earth? Q.27 Q.28 Q.29 Q.30 Although, the value of G is very small, but all the objects near the surface of earth fall towards the earth. Why ? Calculate the force of gravitation between two bodies each of mass 80 kg and placed 16 cm apart. (Take G = 6.67 × 10–11 Nm2/kg2) 1 The mass of Mars is th and its radius is 10 half of that of the earth. Calculate value of g on the surface of Mars. Q.31 Discuss the terms gravitation and gravity with suitable examples. Q.32 State Newton's law of gravitation. State the unit and value of gravitational constant. Q.33 Discuss the various factors on which the value of g depends. Q.34 Compare the gravitational attraction on the earth due to the attraction of sun due to attraction of moon. Given mass of sun = 2 × 1030 kg, mass of moon = 7.35 × 1022 kg, distance of sun from earth = 1.5 × 1011 m, distance of moon from earth = 3.84 × 108m. Q.35 A body weighs 160 N on the surface of the earth. Calculate his weight at a height of 3.6 × 106 m from the surface of the earth. Radius of earth = 6.4 × 106 m. What is the weight of a body whose mass is 25 kg ? ANSWER KEY EXERCISE-1 1. F = G m1 m2 /r2 2. 6.67 × 10–11 Nm2/kg2 3. Nm2/kg2 4. No 5. 9.8 m/s2 6. m/s2 7. g = 8. Decreases 11. Gravitational force 13. Both 9. mg/4 14. decreases 10. poles 15. zero 23. 1.6 × 10–8 N 24. 16 times 25. 490 N 28. 1. 6675 × 10–5N 29. 3.92 m/s2 30. 245 N 34. 1800 : 1 35. 81.9 N GM R2