Answer:
v = 0.84 m/s
Explanation:
given,
R = 12 cm
M (mass of pulley )= 520 g
m  (mass of block)=  20 g
s = 50 cm = 0.5 m
using conservation of energy
Potential energy = Kinetic energy
 [tex]m g h = \dfrac{1}{2}mv^2 + \dfrac{1}{2}I\omega^2[/tex]
  [tex]I_{disk}= \dfrac{1}{2}MR^2[/tex]  and v = r ω
 [tex]m g h = \dfrac{1}{2}mv^2 + \dfrac{1}{2}(\dfrac{1}{2}MR^2)(\dfrac{v}{R})^2[/tex]
 [tex]m g h = \dfrac{1}{2}mv^2 +\dfrac{1}{4}Mv^2[/tex]
 [tex]m g h = \dfrac{1}{2}v^2(m +\dfrac{1}{2}M)[/tex]
 [tex]v=\sqrt{\dfrac{2mgh}{m + 0.5 M}}[/tex]
 [tex]v=\sqrt{\dfrac{2\times 0.020 \times 9.8 \times 0.5}{0.02 + 0.5\times 0.52}}[/tex]
   v = √0.7
   v = 0.84 m/s
