A block of mass 2 kg is attached to a massless rod of length 1/π m on a horizontal surface (μ = 0.1). A constant tangential force maintains uniform angular speed. Find work (J) done during a 90° rotation, g = 10 m s⁻².
Physics · Mixed Chapter
JEE Main Practice

Question

A block of mass 2 kg is attached to a massless rod of length 1/π m on a horizontal surface (μ = 0.1). A constant tangential force maintains uniform angular speed. Find work (J) done during a 90° rotation, g = 10 m s⁻².

Physics · Mixed Chapter

G1 Physics · Accepted Answer

Step 1 — Block moves on circle with constant speed; the external tangential force balances kinetic friction F = μmg. Step 2 — F = 0.1 × 2 × 10 = 2 N. Step 3 — Circular-arc path over 90° is s = rθ = (1/π)(π/2) = 1/2 m. Step 4 — Work W = Fs = 2 × 1/2 = 1 J.