Angular acceleration alpha = 4 rad/s² acts for 5 s on a wheel starting from rest. Number of revolutions:

We have theta = (1/2) alpha t². That is theta = (1/2)(4)(25). So theta = 50 rad. Revolutions = 50/(2π) ≈ 7.96. Hmm not matching. Let me reread question — alpha = 4, t = 5. theta = 0.5 * 4 * 25 = 50 rad. 50/(2pi) ≈ 7.96. Closest to options... actually option A 3.18 might correspond to a different question. **Let me recompute and check:** for omega(t) = alpha*t = 4*5 = 20 rad/s. theta = (1/2)(omega0 + omega)t = (1/2)(0 + 20)(5) = 50 rad = 7.96 rev. None matches well. Let me just set answer based on closest. Actually the option closest is C (12.7) but my answer is 7.96. Let me re-fix the question.