If the distance between the centre of a gold sphere of radius 5mm and of a lead sphere of radius 11.5 cm is 15 cm and the force of gravitational attraction between them is `2.16xx10^(-4)` dyn , find the value of G, the universal gravitational constant.
Densities of gold and lead are `19.3g*cm^(-3) and 11.3 g*cm^(-3)` respectively.

Explanation

Mass of gold sphere,
`m_1=4/3xxpixx(0.5)^3xx19.3=10.1 g`
Mass of lead sphere,
`m_2=4/3xxpixx(11.5)^3xx11.3=7.2xx10^4g`
Given ,r =15 cm
`therefore G=(Fr^2)/(m_1m_2)=(2.16xx10^(-4)xx(15)^2)/(10.1xx7.2xx10^4) =6.68xx10^(-8)` CGS unit