5.1: Find the gravitational force of attraction between two spheres each of mass 1000 kg. The distance between the centres of the spheres is 0.5 m. Ans. (2.67 x10⁻⁴N)


5.2: The gravitational force between two identical lead spheres kept at 1 m apart is 0.006673 N. Find their masses. Ans. (10,000 kg each)


5.3: Find the acceleration due to gravity on the surface of the Mars. The mass of Mars is 6.42x10²³ kg and its radius is 3370 km. Ans. (3.77 ms⁻²)


5.4: The acceleration due to gravity on the surface of moon is 1.62 ms⁻². The radius of moon is 1740 km. Find the mass of moon. Ans. (7.35x10²² kg)


5.5: Calculate the value of g at a height of 3600 km above the surface of the Earth. Ans. (4.0 ms⁻²) 



5.6: Find the value of g due to the Earth at geostationary satellite. The radius of the geostationary orbit is 48700 km. Ans. (0.17 ms⁻²)


5.7: The value of g is 4.0 ms⁻² at a distance of 10,000 km from the centre of the Earth. Find the mass of the Earth. Ans. (5.99x10²⁴ kg)


5.8: At what altitude the value of g would become one fourth than on the surface of the Earth? Ans. (One Earth's radius)

5.9: A polar satellite is launched at 850 km above Earth. Find its orbital speed. Ans. (7431 ms⁻¹)


5.10: A communication satellite is launched at 42000 km above Earth. Find its orbital speed. Ans. (2876 ms⁻¹)