Answer:
Option (B)
Explanation:
Let m be the mass of solid disc.
initial frequency, fo = 500 rpm = 8.33 rps
initial angular velocity, ωo = 2 x 3.14 x 8.33 = 52.33 rad/s
final angular velocity, ω = 0 rad/s
Work done = change in kinetic energy
Let I be the moment of inertia of the disc
Initial kinetic energy
[tex]K_{1}=0.5 \times I \times \omega ^{2}[/tex]
[tex]K_{1}=0.5 \times I \times \52.33 ^{2}[/tex]
K1 = 1369.2 I
Final kinetic energy
[tex]K_{2}=0.5 \times I \times \omega_{0}^{2}[/tex]
K2 = 0
Change in Kinetic energy = 1369.2 I
[tex]I = 0.5 mr^{2}=0.5 \times m \times 1.2 \times 1.2=0.72 m[/tex]
So, Work done
2.3 x 1000 = 1369.2 x 0.72 m
2300 = 985.82 m
m = 2.3 kg
Option (B)
