Find the work done in brigning three particles each having a mass of 100 g, from large distances to the vertices of an equilateal triangle of side 20 cm.

Explanation

When the separation are large the gravitatioN/Al potential energy is zero. When the particles are brought at the vertices of the triangle ABC, three pairs AB, BC and CA are formed The potential energy of each pair is `Gm_1 m_2/r` and hence the total potential energy becomes
`U=3xx[-(Gm_1m_2)/r]`
`=3xx[-(6.67xx10^-11N-m^2/kg^2xx(0.1kg)xx(0.1kg))/(0.20m)]`
=-1.0xx10^-11J`
The work done by the gravitatioN/Al forces is `W=-U=1.0xx106-11J`. If the particles are brought by some exterN/Al agency without changing the kinetic energy, the work done by the exterN/Al agency is equal to the change in potential energy `=1.0xx10^-11J`.