physics
posted by adan .
an airplane propeller slows from an initial angular speed of 12.5rev/s to a final angular speed of 5rev/s during the process the propeller rotates through 21 rev. find the angular acceleration of the propeller if in radians per second squared, assuming its constant?

A 38.0kg crate rests on a horizontal floor, and a 72.8kg person is standing on the crate. Determine the magnitude of the normal force that (a) the floor exerts on the crate and (b) the crate exerts on the person.