Answer:
[tex]\omega_f = 3.46\pi[/tex]
Explanation:
As we know that there is no external torque on the system of disc and the sand
so the angular momentum of the system will remains conserved
so here we can say
[tex]L_i = L_f[/tex]
[tex]I_o\omega = (I_o + mr^2)\omega_f[/tex]
here we know that
[tex]I_o = \frac{1}{2}mR^2[/tex]
[tex]I_o = \frac{1}{2}(27.7)(1.60)^2 = 35.46 kg m^2[/tex]
Now from above equation
[tex]35.46(4\pi) = (35.46 + 2.47(1.5^2))\omega_f[/tex]
[tex]35.46(4\pi) = 41.02\omega_f[/tex]
[tex]\omega_f = 3.46\pi[/tex]