Physics Elena please help!
posted by Stan on .
A coin rests 18.0 cm from the center of a turntable. The coefficient of static friction between the coin and turntable surface is 0.420. The turntable starts from rest at t = 0 and rotates with a constant angular acceleration of 0.650 rad/s2. (a) After 3.00 s, what is the angular velocity of the turntable? (b) At what speed will the coin start to slip? (c) After what period of time will the coin start to slip on the turntable?

(a) ω₃=ε•t₃ =0.65•3 =1.95 rad/s
(b) ma=F(fr)
centripetal acceleration a=v²/R =ω²R
F(fr) =μmg
m ω²R= μmg
ω=sqrt(μg/R)=sqrt(0.42•9.8/0.18)=4.78 rad/s
(c) ω =ε•t
t= ω/ε=4.78/ 0.65=7.35 s