Torque equilibrium in an overhanging beam

Steps:

• Position supports with P left at 0, Q at distance $l$, R at $2l$; person starts at $s = 2l$ from P, moves to $s = l$.
• Vertical equilibrium: $F_P + F_Q = Mg + mg$ (constant total weight).
• Torque about Q: $F_P \cdot l = -mg \cdot (s - l)$ (clockwise person torque balanced by counterclockwise from negative $F_P$).
• As $s$ decreases toward $l$, moment arm $(s - l)$ shrinks, so $|F_P|$ (initially mg) decreases to 0; $F_Q$ then decreases from ~2mg to mg.

Why A is correct:

• Magnitudes decrease per torque balance: shorter lever arm reduces counter-torque needed at P and shared load at Q (Newton's laws of equilibrium).

Why the others are wrong:

• B: $F_Q$ magnitude decreases, not increases.
• C: $|F_P|$ (downward) decreases, not increases.
• D: Neither force magnitude increases.

Final answer: A