Answer:
[tex]r = 1.22 m[/tex]
Explanation:
As we know that block will not slip on the rotating disc then we will have
Friction force = centripetal Force
so here we will have
[tex]F_f = m\omega^2 r[/tex]
Here we know that
[tex]F_f = \mu N[/tex]
so we have
[tex]N = mg[/tex]
[tex]F_f = \mu mg[/tex]
[tex]m\omega^2 r = \mu mg[/tex]
[tex]r = \frac{\mu g}{\omega^2}[/tex]
[tex]r = \frac{0.78\times 9.81}{2.5^2}[/tex]
[tex]r = 1.22 m[/tex]