Physics
posted by DL .
What is the angular momentum of a 2.4 kg uniform cylindrical grinding wheel of radius 12 cm when rotating at 1800 rpm?
How much torque is required to stop it in 4.0 s?

Convert 1800 rpm to radians per second and call it w. (It texts, it's usually a Greek lower case omega)
The angular momentum is I w, where I is the moment of inertia. Use units of kg m^2/s
For a solid cylinder of mass M and radius R, I = (1/2) M R^2.
The torque L required to stop in time T is I w/T. The units will be newton meters or kg m^2/s^2 (same thing)