Adiabatic superbubble similarity solution 2026-10-05
For constant injected power and ambient mass density , dimensional analysis gives . In a similarity solution, set , , and . The strong-shock values on the inner side of are and .
Hydrodynamic coarsening crossover scales 2026-10-06
Under single-length dynamical scaling of binary-fluid coarsening, mass density , dynamic viscosity and surface tension determine the displayed unique length and time scales by dimensional analysis. Writing reduces the force-density estimate to . Resistive and driving terms need opposite signed geometric coefficients. Viscous hydrodynamic coarsening has and inertial hydrodynamic coarsening has . These follow respectively from density-independent and viscosity-independent powers in . They require thin interfaces, statistically self-similar bicontinuous domains, dominant advection and no additional relevant macroscopic scales. A degeneracy in the signed inertial coefficients can invalidate the pure-power force balance without invalidating the dimensional calculation.
Jet length 2026-10-05
For source kinematic momentum flux and buoyancy flux , dimensional analysis gives . Under constant Batchelor entrainment, the actual turning length also contains an entrainment coefficient factor of order .
Past exam of the mathematics course of the University of Cambridge 2007 ia Paper 4 9C i Solution Created 2026-09-24 Updated 2026-09-24
Past exam of the mathematics course of the University of Cambridge 2008 ia Paper 4 9B Solution Created 2026-09-24 Updated 2026-09-24
Past exam of the mathematics course of the University of Cambridge 2009 ia Paper 4 3A Solution Created 2026-09-24 Updated 2026-09-24
Past exam of the mathematics course of the University of Cambridge 2015 ia Paper 4 9C Solution Created 2026-09-24 Updated 2026-10-06
Outside a spherical Earth the gravitational field is the field of its total mass at the center, by the shell theorem. Since , the inverse-square force on the upward radial trajectory givesThe independent dimensional inputs are , of dimensions . A dimensionless monomial in them must be a power of . Thus dimensional analysis givesFor a finite turning height and time, assume , equivalently . This escape velocity restriction is implicit in the requested maximum-height formulas.
The conservation of energy, per unit particle mass, issoThe numerator vanishes at the turning point, givingOn ascent , and integrating givesThe upper endpoint has an integrable inverse-square-root singularity. Set , use and , and note . The result isFor small , and , recovering and . At the particle escapes marginally and has no finite maximum; for it escapes with nonzero asymptotic speed. The finite-turning formulas must not be extended to those cases.