For a small sphere falling through a viscous fluid, how does its terminal velocity depend on its radius r?
Correct answer D. It is proportional to r²
Explanation
Equating weight minus upthrust to 6πηrv gives vₜ = 2r²(ρ − σ)g/9η. Weight grows as r³ while drag grows as r, so terminal velocity is proportional to r².
Answer checked How we write and check questions
Discussion