Answer:
0.62 rad/s
Explanation:
Angular momentum is conserved.
I₁ ω₁ = I₂ ω₂
where I is moment of inertia and ω is angular velocity.
The total moment of inertia is the sum of the platform's inertia and the boy's.
(I + m r₁²) ω₁ = (I + m r₂²) ω₂
Given I = 1000 kg m², m = 50 kg, r₁ = 4.0 m, r₂ = 3.0 m, and ω₁ = 0.5 rad/s:
(1000 + 50 (4.0)²) (0.5) = (1000 + 50 (3.0)²) ω₂
900 = 1450 ω₂
ω₂ = 0.62 rad/s
