A sliding block of base area A = 100 cm² travels over oil film thickness h = 0.1 mm and viscosity η = 1 poise; it is drawn by hanging mass m = 2 kg. Find steady speed (m s⁻¹). [See Image.]
Physics · Mixed Chapter
JEE Main Practice

Question

A sliding block of base area A = 100 cm² travels over oil film thickness h = 0.1 mm and viscosity η = 1 poise; it is drawn by hanging mass m = 2 kg. Find steady speed (m s⁻¹). [See Image.]

G1 Physics · Accepted Answer

Step 1 — In steady motion, block velocity is constant and viscous resistance balances hanging weight: ηAv/h = mg. Step 2 — Unit conversion: η = 1 poise = 0.1 Pa s; A = 100 cm² = 0.01 m²; h = 0.1 mm = 10⁻⁴ m. Step 3 — v = mgh/(ηA) = 2 × 10 × 10⁻⁴/(0.1 × 0.01). Step 4 — v = 2 m s⁻¹.