A spherical metal ball (of density \( \rho_s \) and diameter \( D \)), attached to a string, is exposed to a crossflow (of velocity \( U_\infty \)) of a viscous fluid (of viscosity \( \mu \) and density \( \rho_f \)). Due to the crossflow, the string makes an angle of inclination \( \theta \) with the top surface as shown in the figure. The acceleration due to gravity is denoted by \( g \). For this flow, Reynolds number, \( \text{Re} = \frac{\rho_f U_\infty D}{\mu} \ll 1 \) and buoyancy force in the fluid is negligible compared to viscous force. Assuming the string to be weightless and offering negligible drag, the expression for \( \theta \) is
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