Introduction to Classical Mechanics · Problem 12.11
Relativity (Dynamics) — Morin
Physics — Mechanics · relativistic-rocket-motion
Problem
A dustpan of mass M is given an initial relativistic speed. It gathers up dust with mass density λ per unit length on the floor (as measured in the lab frame). At the instant the speed is v, find the rate (as measured in the lab frame) at which the mass of the dustpan-plus-dust-inside system is increasing.