Physics · GRAVITATION

In Cavendish's experiment to measure \( G \), a bar of length \( L \) connects two small lead spheres each of mass \( m \). Two large spheres each of mass \( M \) are placed at a separation \( d \) from the small spheres. If the restoring couple per unit angle of twist of the suspension wire is \( \tau_0 \) and the angle of deflection is \( \theta \), what is the equilibrium relation?

1. \( 2G\frac{Mm}{d^2} L = \tau_0 \theta \)
2. \( G\frac{Mm}{d^2} L = \tau_0 \theta \)
3. \( G\frac{Mm}{d} L^2 = \tau_0 \theta \)
4. \( G\frac{Mm}{d^2} = \tau_0 \theta L \)