Question

determine the angular acceleration of a rotating body which shows down from 500 r.m.p to rest in 10 seconds

Answer 1

body makes 500 rev in 60 sec
So, it makes 25/3 rev in 1 sec : ω₀=25/3  rev s⁻¹

ω=ω₀+αt
0=25/3+α10
-25/3=10α
α=-25/30=-5/6 rev s⁻²

Answer 2

ω1= 2πn1                                   t=10s

       =2π×500÷60                    α= ω2-ω1/t

        =50π/3 rad                         =0-50π/3÷10

ω2= 2πn2                                    =-5π/3

     = 2π×0

       =0 rad                              angular acceleration=-5π/3