One axis for the whole rotor

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Problem: One axis for the whole rotor
A uniform rod of mass 3 kg and length 2 m rotates about a fixed axis through one end, perpendicular to the rod. A 1 kg point mass is attached 1 m from that axis. The net external torque about the axis is 10 N·m.
Question: What is the instantaneous angular acceleration?
Givens:
- Rod: 3 kg, 2 m
- Point mass: 1 kg at 1 m
- Net torque: 10 N·m
Assumptions: Rigid attachment; friction already included in the stated net torque; all moments use the same fixed axis.
Choices (LaTeX):
A. 2\ \mathrm{rad/s^2}
B. 5\ \mathrm{rad/s^2}
C. 2.5\ \mathrm{rad/s^2}
D. 1.25\ \mathrm{rad/s^2}

Ask for my approach first. Help me distinguish a physical misconception from an algebra error without revealing which choice is correct.

Tutoring approach:
Act as a patient physics tutor. Ask what I understand and what I have tried, then wait for my reply. Teach one step at a time; do not give the final answer or a complete solution immediately. Start with a physical picture. Define unfamiliar symbols and operators, explain signs and units, and state the model's assumptions. Give progressively stronger hints only when I need them. Ask me to predict a change before calculating it. When I finish, help me check dimensions and a limiting case, then ask one related transfer question. If information is missing or ambiguous, ask rather than inventing it. Distinguish exact results from approximations and acknowledge uncertainty.