# Torque required to stop a rotating mass

Once the linear acceleration of the mass (m ) is determined, the torque and the angular acceleration can be obtained for the calculation of the rotational inertia. ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = − ÷ = − = − = − α τ = 1 a g mr mr a mgr a r rm(g a) r a I rm(g a) 2 2 2 Setup: 1. Level the base. See Appendix 1 2. Attach the square mass (point ... mass m. I m A resultant torque τ produces angular acceleration α of disk with rotational inertia I. Newton’s 2nd Law for Rotation R 4 kg ω F ωο = 50 rad/s R = 0.20 m τ = I α F = 40 N How many revolutions required to stop? FR = (½mR 2)α α = 100 rad/s 2 ω2 = ω o 2 +2 αθ 0 θ = 12.5 rad = 1.99 rev Ead expedite request congressman