1. The problem statement, all variables and given/known data A wheel of moment of inertia 5×10-3kg-m2 is making 20 rev/s. Find the torque required to stop it in 10s is (A) 2π×10-2Nm (B) 2π×102Nm (C) 4π×10-2Nm (D) 4π×102Nm Answer - (A). 2. Relevant equations ω=2πƒ (ƒ=frequency) Power (P) = Γω. P = W/t. W = ΔK.E. = (1/2)Iω2. 3. The attempt at a solution The power delivered is equal to the rate of doing work which is equal to the change in rotational kinetic energy. On calculating, I get the final answer as 10-2πN.m. Kindly help.