Fig. 10.7 — Force measurement from equilibrium distribution

Schematic procedure for measuring a force F(z) by the equilibrium distribution method. From (a) the measured equilibrium probability distribution ρ(z) of a particle, one obtains (b) the potential energy distribution U(z) = −k_BT ln ρ(z), which then gives (c) the force F(z) = − d_zU(z) [Eq. (10.26)].