The magnitude of the angular acceleration of the pendulum at the moment of release is; α = 18.45 rad/s²
We are given;
Mass of rod; m = 1 kg
Length of rod; L = 49.8 cm = 0.498 m
Mass of Disk; M = 4 kg
Radius of disk; r = 24.9 cm = 0.249 m
Let us first calculate the torque acting from the formula;
τ = mg(L/2) + MgL
Thus;
τ = (1 × 9.8 × (0.498/2)) + (4 × 9.8 × 0.498)
τ = 21.96 N.m
Using parallel axis theorem, we can find the moment of inertia about the given axis as;
I = (mL²/3) + ½MR² + ML²
Plugging in the relevant values gives;
I = (1 * 0.498²/3) + ½(4 * 0.249²) + (4 * 0.498²)
I = 1.19 kg.m²
The angular acceleration is given by the formula;
α = I/τ
α = 21.96/1.19
α = 18.45 rad/s²
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