JEE Main202116 Mar 2021Morning ShiftPhysicsRotational MotionActual
Consider a 20 kg uniform circular disk of radius 0 . 2 m . It is pin supported at its center and is at rest initially. The disk is acted upon by a constant force F = 20 N through a massless string wrapped around its periphery as shown in the figure. Suppose the disk makes n number of revolutions to attain an angular speed of 50 rad s - 1 . The value of n , to the nearest integer, is _______ . [Given : In one complete
Correct answer
0
Step-by-step solution
α = τ I = F . R . m R 2 / 2 = 2   F m R α = 2 × 200 20 × 0 . 2 = 10   rad / s 2 ω 2 = ω 0 2 + 2 α Δ θ 50 2 = 0 2 + 2 10 Δ θ ⇒ Δ θ = 2500 20 Δ θ = 125   rad No. of = 125 2 π ≈ 20 revolution