Two identical solid lead spheres each have a diameter of 20cm. The density of lead is 11.3g/cm3.
a. (i) Calculate the mass of one sphere. (Use π=3.14.)
b. (ii) The spheres are placed so that they just touch each other. Find the magnitude of the gravitational force between them in this position.
c. (iii) The spheres are now moved so that the distance between their centres becomes 40cm. Calculate the new magnitude of the gravitational force.
d. (iv) Determine the ratio of the forces obtained in parts (iii) and (ii) and explain the result briefly.