Auestion 2 A thin disk with a radius of 2 feet thickness of

Auestion 2 A thin disk, with a radius of 2 feet, thickness of 0.2 feet, and density of 50 lb/ft 3 (HINT: for mass convert lb to slugs), is spinning at 75 rotations per minute. If the disk is to come to a complete stop in 5 seconds, what is the magnitude of the force that needs to be applied as shown in the picture below? (,3%m? )

Solution

1. Force F = mw²/r

m = density * volume = 50*3.14*2*2*0.2 =125.6 lb

F = 125.6*(75*2*3.14/60)²/2 =3869.89 N