The Newton’s problem assuming non-constant density of the fluid López Camino, Rafael Newton problem Minimum resistance Banach fixed point theorem This paper investigates the Newton’s problem of minimal resistance for a body moving through a fluid whose density decreases exponentially with altitude. We prove the local existence and regularity of radial solutions u (r) satisfying the initial conditions u(0)=u(0)=0 using a fixed point theorem. We show that the maximal domain of the solution is finite, (0,rM), terminating at a critical slope u(rM)= 1V 2026-03-24T12:27:09Z 2026-03-24T12:27:09Z 2026-06 journal article López, R. (2026). The Newton’s problem assuming non-constant density of the fluid. Applied Mathematics Letters, 177(109901), 109901. https://doi.org/10.1016/j.aml.2026.109901 https://hdl.handle.net/10481/112433 10.1016/j.aml.2026.109901 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional Elsevier