Moderate -0.3 This is a straightforward application of rotational dynamics using τ = Iα with constant torque. Students need to find torque (F × r), calculate angular deceleration, then use kinematics (ω = ω₀ + αt). It's slightly easier than average because it's a direct plug-and-chug problem with clearly given values and no conceptual complications, though the rotational context makes it non-trivial.
A circular flywheel of radius 0.3 m, with moment of inertia about its axis 18 kg m\(^2\), is rotating freely with angular speed 6 rad s\(^{-1}\). A tangential force of constant magnitude 48 N is applied to the rim of the flywheel, in order to slow the flywheel down. Find the time taken for the angular speed of the flywheel to be reduced to 2 rad s\(^{-1}\). [4]
A circular flywheel of radius 0.3 m, with moment of inertia about its axis 18 kg m$^2$, is rotating freely with angular speed 6 rad s$^{-1}$. A tangential force of constant magnitude 48 N is applied to the rim of the flywheel, in order to slow the flywheel down. Find the time taken for the angular speed of the flywheel to be reduced to 2 rad s$^{-1}$. [4]
\hfill \mbox{\textit{CAIE FP2 2012 Q1 [4]}}